ForceMode (WIP)

Cargo.lock

@@ -188,13 +188,6 @@ dependencies = [
  "generic-array",
 ]
 
-[[package]]
-name = "boxing"
-version = "0.1.3"
-dependencies = [
- "sptr",
-]
-
 [[package]]
 name = "bstr"
 version = "1.12.1"
@@ -798,7 +791,6 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "base64",
- "boxing",
  "bumpalo",
  "bzip2",
  "clap",
@@ -833,6 +825,7 @@ dependencies = [
  "sha2",
  "small-map",
  "smallvec",
+ "sptr",
  "string-interner",
  "tap",
  "tar",

Cargo.toml

@@ -2,7 +2,6 @@
 resolver = "3"
 members = [
     "fix",
-    "boxing",
 ]
 
 [profile.profiling]

boxing/Cargo.toml

@@ -1,8 +0,0 @@
-[package]
-name = "boxing"
-version = "0.1.3"
-edition = "2021"
-description = "NaN-boxing primitives (local fork with bool fix)"
-
-[dependencies]
-sptr = "0.3"

boxing/src/lib.rs

@@ -1,2 +0,0 @@
-pub mod nan;
-mod utils;

boxing/src/nan.rs

@@ -1,7 +0,0 @@
-pub mod raw;
-
-pub use raw::RawBox;
-
-const SIGN_MASK: u64 = 0x7FFF_FFFF_FFFF_FFFF;
-const QUIET_NAN: u64 = 0x7FF8_0000_0000_0000;
-const NEG_QUIET_NAN: u64 = 0xFFF8_0000_0000_0000;

boxing/src/utils.rs

@@ -1,16 +0,0 @@
-pub trait ArrayExt<const LEN: usize> {
-    type Elem;
-
-    fn truncate_to<const M: usize>(self) -> [Self::Elem; M];
-}
-
-impl<T: Default + Copy, const N: usize> ArrayExt<N> for [T; N] {
-    type Elem = T;
-
-    fn truncate_to<const M: usize>(self) -> [Self::Elem; M] {
-        let copy_len = usize::min(N, M);
-        let mut out = [T::default(); M];
-        out[0..copy_len].copy_from_slice(&self[0..copy_len]);
-        out
-    }
-}

fix/Cargo.toml

@@ -79,7 +79,7 @@ tap = "1.0.1"
 
 ghost-cell = "0.2"
 colored = "3.1"
-boxing = { path = "../boxing" }
+sptr = "0.3"
 sealed = "0.6"
 small-map = "0.1"
 smallvec = "1.15"

fix/src/boxing.rs

@@ -1,11 +1,28 @@
-use super::{NEG_QUIET_NAN, QUIET_NAN, SIGN_MASK};
-use crate::utils::ArrayExt;
-use sptr::Strict;
 use std::fmt;
-use std::mem::ManuallyDrop;
 use std::num::NonZeroU8;
 
-pub trait RawStore: Sized {
+use sptr::Strict;
+
+const SIGN_MASK: u64 = 0x7FFF_FFFF_FFFF_FFFF;
+const QUIET_NAN: u64 = 0x7FF8_0000_0000_0000;
+const NEG_QUIET_NAN: u64 = 0xFFF8_0000_0000_0000;
+
+pub(crate) trait ArrayExt<const LEN: usize> {
+    type Elem;
+    fn truncate_to<const M: usize>(self) -> [Self::Elem; M];
+}
+
+impl<T: Default + Copy, const N: usize> ArrayExt<N> for [T; N] {
+    type Elem = T;
+    fn truncate_to<const M: usize>(self) -> [Self::Elem; M] {
+        let copy_len = usize::min(N, M);
+        let mut out = [T::default(); M];
+        out[0..copy_len].copy_from_slice(&self[0..copy_len]);
+        out
+    }
+}
+
+pub(crate) trait RawStore: Sized {
     fn to_val(self, value: &mut Value);
     fn from_val(value: &Value) -> Self;
 }
@@ -138,18 +155,18 @@ enum TagVal {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq)]
-pub struct RawTag(TagVal);
+pub(crate) struct RawTag(TagVal);
 
 impl RawTag {
     #[inline]
     #[must_use]
-    pub fn new(neg: bool, val: NonZeroU8) -> RawTag {
+    pub(crate) fn new(neg: bool, val: NonZeroU8) -> RawTag {
         unsafe { Self::new_unchecked(neg, val.get() & 0x07) }
     }
 
     #[inline]
     #[must_use]
-    pub fn new_checked(neg: bool, val: u8) -> Option<RawTag> {
+    pub(crate) fn new_checked(neg: bool, val: u8) -> Option<RawTag> {
         Some(RawTag(match (neg, val) {
             (false, 1) => TagVal::_P1,
             (false, 2) => TagVal::_P2,
@@ -176,7 +193,7 @@ impl RawTag {
     /// `val` must be in the range `1..8`
     #[inline]
     #[must_use]
-    pub unsafe fn new_unchecked(neg: bool, val: u8) -> RawTag {
+    pub(crate) unsafe fn new_unchecked(neg: bool, val: u8) -> RawTag {
         RawTag(match (neg, val) {
             (false, 1) => TagVal::_P1,
             (false, 2) => TagVal::_P2,
@@ -200,7 +217,7 @@ impl RawTag {
 
     #[inline]
     #[must_use]
-    pub fn is_neg(self) -> bool {
+    pub(crate) fn is_neg(self) -> bool {
         matches!(self.0, |TagVal::_N1| TagVal::_N2
             | TagVal::_N3
             | TagVal::_N4
@@ -211,7 +228,7 @@ impl RawTag {
 
     #[inline]
     #[must_use]
-    pub fn val(self) -> NonZeroU8 {
+    pub(crate) fn val(self) -> NonZeroU8 {
         match self.0 {
             TagVal::_P1 | TagVal::_N1 => NonZeroU8::MIN,
             TagVal::_P2 | TagVal::_N2 => NonZeroU8::MIN.saturating_add(1),
@@ -225,7 +242,7 @@ impl RawTag {
 
     #[inline]
     #[must_use]
-    pub fn neg_val(self) -> (bool, u8) {
+    pub(crate) fn neg_val(self) -> (bool, u8) {
         match self.0 {
             TagVal::_P1 => (false, 1),
             TagVal::_P2 => (false, 2),
@@ -286,9 +303,9 @@ impl Header {
     }
 }
 
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 #[repr(C, align(8))]
-pub struct Value {
+pub(crate) struct Value {
     #[cfg(target_endian = "big")]
     header: Header,
     data: [u8; 6],
@@ -298,7 +315,7 @@ pub struct Value {
 
 impl Value {
     #[inline]
-    pub fn new(tag: RawTag, data: [u8; 6]) -> Value {
+    pub(crate) fn new(tag: RawTag, data: [u8; 6]) -> Value {
         Value {
             header: Header::new(tag),
             data,
@@ -306,23 +323,23 @@ impl Value {
     }
 
     #[inline]
-    pub fn empty(tag: RawTag) -> Value {
+    pub(crate) fn empty(tag: RawTag) -> Value {
         Value::new(tag, [0; 6])
     }
 
-    pub fn store<T: RawStore>(tag: RawTag, val: T) -> Value {
+    pub(crate) fn store<T: RawStore>(tag: RawTag, val: T) -> Value {
         let mut v = Value::new(tag, [0; 6]);
         T::to_val(val, &mut v);
         v
     }
 
-    pub fn load<T: RawStore>(self) -> T {
+    pub(crate) fn load<T: RawStore>(self) -> T {
         T::from_val(&self)
     }
 
     #[inline]
     #[must_use]
-    pub fn tag(&self) -> RawTag {
+    pub(crate) fn tag(&self) -> RawTag {
         self.header.tag()
     }
 
@@ -332,41 +349,42 @@ impl Value {
     }
 
     #[inline]
-    pub fn set_data(&mut self, val: [u8; 6]) {
+    pub(crate) fn set_data(&mut self, val: [u8; 6]) {
         self.data = val;
     }
 
     #[inline]
     #[must_use]
-    pub fn data(&self) -> &[u8; 6] {
+    pub(crate) fn data(&self) -> &[u8; 6] {
         &self.data
     }
 
     #[inline]
     #[must_use]
-    pub fn data_mut(&mut self) -> &mut [u8; 6] {
+    pub(crate) fn data_mut(&mut self) -> &mut [u8; 6] {
         &mut self.data
     }
 
     #[inline]
     #[must_use]
-    pub unsafe fn whole(&self) -> &[u8; 8] {
+    unsafe fn whole(&self) -> &[u8; 8] {
         let ptr = (self as *const Value).cast::<[u8; 8]>();
         unsafe { &*ptr }
     }
 
     #[inline]
     #[must_use]
-    pub unsafe fn whole_mut(&mut self) -> &mut [u8; 8] {
+    unsafe fn whole_mut(&mut self) -> &mut [u8; 8] {
         let ptr = (self as *mut Value).cast::<[u8; 8]>();
         unsafe { &mut *ptr }
     }
 }
 
 #[repr(C)]
-pub union RawBox {
+#[derive(Copy, Clone)]
+pub(crate) union RawBox {
     float: f64,
-    value: ManuallyDrop<Value>,
+    value: Value,
     bits: u64,
     #[cfg(target_pointer_width = "64")]
     ptr: *const (),
@@ -377,7 +395,7 @@ pub union RawBox {
 impl RawBox {
     #[inline]
     #[must_use]
-    pub fn from_float(val: f64) -> RawBox {
+    pub(crate) fn from_float(val: f64) -> RawBox {
         match (val.is_nan(), val.is_sign_positive()) {
             (true, true) => RawBox {
                 float: f64::from_bits(QUIET_NAN),
@@ -391,15 +409,13 @@ impl RawBox {
 
     #[inline]
     #[must_use]
-    pub fn from_value(value: Value) -> RawBox {
-        RawBox {
-            value: ManuallyDrop::new(value),
-        }
+    pub(crate) fn from_value(value: Value) -> RawBox {
+        RawBox { value }
     }
 
     #[inline]
     #[must_use]
-    pub fn tag(&self) -> Option<RawTag> {
+    pub(crate) fn tag(&self) -> Option<RawTag> {
         if self.is_value() {
             Some(unsafe { self.value.tag() })
         } else {
@@ -409,19 +425,19 @@ impl RawBox {
 
     #[inline]
     #[must_use]
-    pub fn is_float(&self) -> bool {
+    pub(crate) fn is_float(&self) -> bool {
         (unsafe { !self.float.is_nan() } || unsafe { self.bits & SIGN_MASK == QUIET_NAN })
     }
 
     #[inline]
     #[must_use]
-    pub fn is_value(&self) -> bool {
+    pub(crate) fn is_value(&self) -> bool {
         (unsafe { self.float.is_nan() } && unsafe { self.bits & SIGN_MASK != QUIET_NAN })
     }
 
     #[inline]
     #[must_use]
-    pub fn float(&self) -> Option<&f64> {
+    pub(crate) fn float(&self) -> Option<&f64> {
         if self.is_float() {
             Some(unsafe { &self.float })
         } else {
@@ -431,7 +447,7 @@ impl RawBox {
 
     #[inline]
     #[must_use]
-    pub fn value(&self) -> Option<&Value> {
+    pub(crate) fn value(&self) -> Option<&Value> {
         if self.is_value() {
             Some(unsafe { &self.value })
         } else {
@@ -440,20 +456,11 @@ impl RawBox {
     }
 
     #[inline]
-    pub fn into_float_unchecked(self) -> f64 {
+    pub(crate) fn into_float_unchecked(self) -> f64 {
         unsafe { self.float }
     }
 }
 
-impl Clone for RawBox {
-    #[inline]
-    fn clone(&self) -> Self {
-        RawBox {
-            ptr: unsafe { self.ptr },
-        }
-    }
-}
-
 impl fmt::Debug for RawBox {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.float() {

fix/src/error.rs

@@ -125,8 +125,6 @@ pub enum Error {
         #[label("error occurred here")]
         span: Option<SourceSpan>,
         message: String,
-        #[help]
-        js_backtrace: Option<String>,
         #[related]
         stack_trace: Vec<StackFrame>,
     },
@@ -163,12 +161,11 @@ impl Error {
         .into()
     }
 
-    pub fn eval_error(msg: String, backtrace: Option<String>) -> Box<Self> {
+    pub fn eval_error(msg: impl Into<String>) -> Box<Self> {
         Error::EvalError {
             src: None,
             span: None,
-            message: msg,
-            js_backtrace: backtrace,
+            message: msg.into(),
             stack_trace: Vec::new(),
         }
         .into()

fix/src/lib.rs

@@ -1,6 +1,7 @@
 #![warn(clippy::unwrap_used)]
 #![allow(dead_code)]
 
+mod boxing;
 pub mod error;
 pub mod logging;
 pub mod runtime;

fix/src/main.rs

@@ -10,7 +10,7 @@ use rustyline::DefaultEditor;
 use rustyline::error::ReadlineError;
 
 #[derive(Parser)]
-#[command(name = "nix-js", about = "Nix expression evaluator")]
+#[command(name = "fix", about = "Nix expression evaluator")]
 struct Cli {
     #[command(subcommand)]
     command: Command,
@@ -40,8 +40,8 @@ struct ExprSource {
     file: Option<PathBuf>,
 }
 
-fn run_compile(runtime: &mut Runtime, src: ExprSource, silent: bool) -> Result<()> {
-    let src = if let Some(expr) = src.expr {
+fn run_compile(_runtime: &mut Runtime, src: ExprSource, _silent: bool) -> Result<()> {
+    let _src = if let Some(expr) = src.expr {
         Source::new_eval(expr)?
     } else if let Some(file) = src.file {
         Source::new_file(file)?

fix/src/runtime.rs

@@ -12,10 +12,12 @@ use crate::downgrade::{Downgrade as _, DowngradeContext};
 use crate::error::{Error, Result, Source};
 use crate::ir::{ArgId, Ir, IrKey, IrRef, RawIrRef, StringId, ThunkId, ir_content_eq};
 use crate::runtime::builtins::new_builtins_env;
+use crate::runtime::vm::ForceMode;
 use crate::store::{DaemonStore, StoreConfig};
 use crate::value::Symbol;
 
 mod builtins;
+mod primops;
 mod stack;
 mod value;
 mod vm;
@@ -43,6 +45,7 @@ impl Runtime {
         let store = DaemonStore::connect(&config.daemon_socket)?;
 
         Ok(Self {
+            arena: Arena::new(|mc| VM::new(mc, &mut strings)),
             global_env,
             store,
             strings,
@@ -50,25 +53,19 @@ impl Runtime {
             bytecode: Vec::new(),
             sources: Vec::new(),
             spans: Vec::new(),
-            arena: Arena::new(|mc| VM::new(mc)),
         })
     }
 
     pub fn eval(&mut self, source: Source) -> Result<crate::value::Value> {
-        let root = self.downgrade(source, None)?;
-        let ip = crate::codegen::compile_bytecode(root.as_ref(), self);
-        self.run(ip)
+        self.do_eval(source, None, ForceMode::Normal)
     }
 
-    pub fn eval_shallow(&mut self, _source: Source) -> Result<crate::value::Value> {
-        todo!()
+    pub fn eval_shallow(&mut self, source: Source) -> Result<crate::value::Value> {
+        self.do_eval(source, None, ForceMode::Shallow)
     }
 
     pub fn eval_deep(&mut self, source: Source) -> Result<crate::value::Value> {
-        // FIXME: deep
-        let root = self.downgrade(source, None)?;
-        let ip = crate::codegen::compile_bytecode(root.as_ref(), self);
-        self.run(ip)
+        self.do_eval(source, None, ForceMode::Deep)
     }
 
     pub fn eval_repl(
@@ -76,10 +73,18 @@ impl Runtime {
         source: Source,
         scope: &HashSet<StringId>,
     ) -> Result<crate::value::Value> {
-        // FIXME: shallow
-        let root = self.downgrade(source, Some(Scope::Repl(scope)))?;
+        self.do_eval(source, Some(Scope::Repl(scope)), ForceMode::Shallow)
+    }
+
+    fn do_eval<'ctx>(
+        &'ctx mut self,
+        source: Source,
+        extra_scope: Option<Scope<'ctx>>,
+        force_mode: ForceMode,
+    ) -> Result<crate::value::Value> {
+        let root = self.downgrade(source, extra_scope)?;
         let ip = crate::codegen::compile_bytecode(root.as_ref(), self);
-        self.run(ip)
+        self.run(ip, force_mode)
     }
 
     pub fn add_binding(
@@ -108,8 +113,11 @@ impl Runtime {
             bump,
             token,
             strings,
-            source: sources.last().unwrap().clone(),
-            scopes: [Scope::Global(global_env)].into_iter().chain(extra_scope.into_iter()).collect(),
+            source: sources.last().expect("no current source").clone(),
+            scopes: [Scope::Global(global_env)]
+                .into_iter()
+                .chain(extra_scope)
+                .collect(),
             with_scope_count: 0,
             arg_count: 0,
             thunk_count,
@@ -117,7 +125,11 @@ impl Runtime {
         }
     }
 
-    fn downgrade<'a>(&'a mut self, source: Source, extra_scope: Option<Scope<'a>>) -> Result<OwnedIr> {
+    fn downgrade<'a>(
+        &'a mut self,
+        source: Source,
+        extra_scope: Option<Scope<'a>>,
+    ) -> Result<OwnedIr> {
         tracing::debug!("Parsing Nix expression");
 
         self.sources.push(source.clone());
@@ -140,8 +152,10 @@ impl Runtime {
         })
     }
 
-    fn run(&mut self, ip: InstructionPtr) -> Result<crate::value::Value> {
+    fn run(&mut self, ip: InstructionPtr, force_mode: ForceMode) -> Result<crate::value::Value> {
         let mut pc = ip.0;
+        self.arena
+            .mutate_root(|_, vm| vm.set_force_mode(force_mode));
         loop {
             let Runtime {
                 bytecode,
@@ -149,8 +163,7 @@ impl Runtime {
                 arena,
                 ..
             } = self;
-            let action =
-                arena.mutate_root(|mc, root| root.run_batch(bytecode, &mut pc, mc, strings));
+            let action = arena.mutate_root(|mc, vm| vm.run_batch(bytecode, &mut pc, mc, strings));
             match action {
                 Action::NeedGc => {
                     if self.arena.collection_phase() == CollectionPhase::Sweeping {
@@ -496,7 +509,7 @@ impl OwnedIr {
     unsafe fn new(ir: RawIrRef<'_>, bump: Bump) -> Self {
         Self {
             _bump: bump,
-            ir: unsafe { std::mem::transmute::<RawIrRef<'_>, RawIrRef<'static>>(ir) }
+            ir: unsafe { std::mem::transmute::<RawIrRef<'_>, RawIrRef<'static>>(ir) },
         }
     }
 

fix/src/runtime/builtins.rs

@@ -1,11 +1,204 @@
+use gc_arena::Collect;
 use hashbrown::HashMap;
+use num_enum::TryFromPrimitive;
 use string_interner::DefaultStringInterner;
 
+use super::value::*;
 use crate::ir::{Ir, RawIrRef, StringId};
 
+/// Generates both the BUILTINS const table and the BuiltinId enum
+/// from a single source of truth, preventing index desync.
+macro_rules! define_builtins {
+    ($(($name:literal, $variant:ident, $arity:expr)),* $(,)?) => {
+        /// Builtin function registry.
+        /// Array index IS the PrimOp id. (name, arity) pairs.
+        pub(super) const BUILTINS: &[(&str, u8)] = &[
+            $(($name, $arity),)*
+        ];
+
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, TryFromPrimitive, Collect)]
+        #[repr(u8)]
+        #[collect(require_static)]
+        pub(super) enum BuiltinId {
+            $($variant,)*
+        }
+    };
+}
+
+define_builtins! {
+    ("abort",                    Abort,                    1),
+    ("add",                      Add,                      2),
+    ("addErrorContext",          AddErrorContext,           2),
+    ("all",                      All,                      2),
+    ("any",                      Any,                      2),
+    ("appendContext",            AppendContext,             2),
+    ("attrNames",                AttrNames,                1),
+    ("attrValues",               AttrValues,               1),
+    ("baseNameOf",               BaseNameOf,               1),
+    ("bitAnd",                   BitAnd,                   2),
+    ("bitOr",                    BitOr,                    2),
+    ("bitXor",                   BitXor,                   2),
+    ("catAttrs",                 CatAttrs,                 2),
+    ("ceil",                     Ceil,                     1),
+    ("compareVersions",          CompareVersions,          2),
+    ("concatLists",              ConcatLists,              1),
+    ("concatMap",                ConcatMap,                2),
+    ("concatStringsSep",         ConcatStringsSep,         2),
+    ("convertHash",              ConvertHash,              1),
+    ("deepSeq",                  DeepSeq,                  2),
+    ("derivation",               Derivation,               1),
+    ("derivationStrict",         DerivationStrict,         1),
+    ("dirOf",                    DirOf,                    1),
+    ("div",                      Div,                      2),
+    ("elem",                     Elem,                     2),
+    ("elemAt",                   ElemAt,                   2),
+    ("fetchGit",                 FetchGit,                 1),
+    ("fetchMercurial",           FetchMercurial,           1),
+    ("fetchTarball",             FetchTarball,             1),
+    ("fetchTree",                FetchTree,                1),
+    ("fetchurl",                 FetchUrl,                 1),
+    ("filter",                   Filter,                   2),
+    ("filterSource",             FilterSource,             2),
+    ("findFile",                 FindFile,                 2),
+    ("floor",                    Floor,                    1),
+    ("foldl'",                   FoldlStrict,              3),
+    ("fromJSON",                 FromJSON,                 1),
+    ("fromTOML",                 FromTOML,                 1),
+    ("functionArgs",             FunctionArgs,             1),
+    ("genList",                  GenList,                  2),
+    ("genericClosure",           GenericClosure,           1),
+    ("getAttr",                  GetAttr,                  2),
+    ("getContext",               GetContext,               1),
+    ("getEnv",                   GetEnv,                   1),
+    ("groupBy",                  GroupBy,                  2),
+    ("hasAttr",                  HasAttr,                  2),
+    ("hasContext",               HasContext,               1),
+    ("hashFile",                 HashFile,                 2),
+    ("hashString",               HashString,               2),
+    ("head",                     Head,                     1),
+    ("import",                   Import,                   1),
+    ("intersectAttrs",           IntersectAttrs,           2),
+    ("isAttrs",                  IsAttrs,                  1),
+    ("isBool",                   IsBool,                   1),
+    ("isFloat",                  IsFloat,                  1),
+    ("isFunction",               IsFunction,               1),
+    ("isInt",                    IsInt,                    1),
+    ("isList",                   IsList,                   1),
+    ("isNull",                   IsNull,                   1),
+    ("isPath",                   IsPath,                   1),
+    ("isString",                 IsString,                 1),
+    ("length",                   Length,                   1),
+    ("lessThan",                 LessThan,                 2),
+    ("listToAttrs",              ListToAttrs,              1),
+    ("map",                      Map,                      2),
+    ("mapAttrs",                 MapAttrs,                 2),
+    ("match",                    Match,                    2),
+    ("mul",                      Mul,                      2),
+    ("null",                     Null,                     0), // constant, not a function
+    ("parseDrvName",             ParseDrvName,             1),
+    ("partition",                Partition,                2),
+    ("path",                     Path,                     1),
+    ("pathExists",               PathExists,               1),
+    ("placeholder",              Placeholder,              1),
+    ("readDir",                  ReadDir,                  1),
+    ("readFile",                 ReadFile,                 1),
+    ("readFileType",             ReadFileType,             1),
+    ("removeAttrs",              RemoveAttrs,              2),
+    ("replaceStrings",           ReplaceStrings,           3),
+    ("scopedImport",             ScopedImport,             2),
+    ("seq",                      Seq,                      2),
+    ("sort",                     Sort,                     2),
+    ("split",                    Split,                    2),
+    ("splitVersion",             SplitVersion,             1),
+    ("storePath",                StorePath,                1),
+    ("stringLength",             StringLength,             1),
+    ("sub",                      Sub,                      2),
+    ("substring",                Substring,                3),
+    ("tail",                     Tail,                     1),
+    ("throw",                    Throw,                    1),
+    ("toFile",                   ToFile,                   2),
+    ("toJSON",                   ToJSON,                   1),
+    ("toPath",                   ToPath,                   1),
+    ("toString",                 ToString,                 1),
+    ("toXML",                    ToXML,                    1),
+    ("trace",                    Trace,                    2),
+    ("tryEval",                  TryEval,                  1),
+    ("typeOf",                   TypeOf,                   1),
+    ("unsafeDiscardStringContext", UnsafeDiscardStringContext, 1),
+    ("unsafeGetAttrPos",         UnsafeGetAttrPos,         2),
+    ("warn",                     Warn,                     2),
+    ("zipAttrsWith",             ZipAttrsWith,             2),
+    ("break",                    Break,                    1),
+}
+
+/// Names that need to be pre-interned for builtin implementations.
+const EXTRA_INTERN_NAMES: &[&str] = &[
+    "builtins",
+    "currentSystem",
+    "langVersion",
+    "nixVersion",
+    "storeDir",
+    "nixPath",
+    "true",
+    "false",
+    // typeOf return values
+    "int",
+    "float",
+    "bool",
+    "string",
+    "path",
+    "null",
+    "set",
+    "list",
+    "lambda",
+    // attrset keys used by builtins
+    "name",
+    "value",
+    "success",
+    "right",
+    "wrong",
+    "key",
+    "operator",
+    "startSet",
+    "__toString",
+    "outPath",
+    "__functor",
+    "drvPath",
+    "type",
+    "derivation",
+    "version",
+];
+
+/// Returns true if this builtin has lazy argument semantics
+/// (not all args should be forced before dispatch).
+pub(super) fn is_lazy_builtin(id: BuiltinId) -> bool {
+    matches!(
+        id,
+        BuiltinId::Seq
+            | BuiltinId::DeepSeq
+            | BuiltinId::Trace
+            | BuiltinId::Warn
+            | BuiltinId::TryEval
+            | BuiltinId::AddErrorContext
+            | BuiltinId::Break
+    )
+}
+
+/// Intern all builtin names and extra names needed at runtime.
+fn intern_all_builtins(interner: &mut DefaultStringInterner) {
+    for &(name, _) in BUILTINS {
+        interner.get_or_intern(name);
+    }
+    for &name in EXTRA_INTERN_NAMES {
+        interner.get_or_intern(name);
+    }
+}
+
 pub(super) fn new_builtins_env(
     interner: &mut DefaultStringInterner,
 ) -> HashMap<StringId, Ir<'static, RawIrRef<'static>>> {
+    intern_all_builtins(interner);
+
     let mut builtins = HashMap::new();
     let builtins_sym = StringId(interner.get_or_intern("builtins"));
     builtins.insert(builtins_sym, Ir::Builtins);
@@ -49,3 +242,6 @@ pub(super) fn new_builtins_env(
 
     builtins
 }
+
+pub(super) type PrimOpArgs<'gc> = [Value<'gc>; 3];
+pub(super) type PrimOpStrictArgs<'gc> = [StrictValue<'gc>; 3];

fix/src/runtime/primops.rs

@@ -0,0 +1,929 @@
+use gc_arena::{Collect, Gc, Mutation, RefLock};
+use smallvec::SmallVec;
+use string_interner::DefaultStringInterner;
+
+use super::builtins::{BuiltinId, PrimOpArgs, PrimOpStrictArgs};
+use super::value::*;
+use super::vm::{ForceResult, VM, VmError};
+use crate::ir::StringId;
+
+pub(super) enum BuiltinResult<'gc> {
+    Done(Value<'gc>),
+    Force(BuiltinState<'gc>, Value<'gc>),
+    Call(BuiltinState<'gc>, StrictValue<'gc>, Value<'gc>),
+    CallAndForce(BuiltinState<'gc>, StrictValue<'gc>, Value<'gc>),
+    Error(VmError),
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub(super) enum BuiltinState<'gc> {
+    FoldlStrict(FoldlStrict<'gc>),
+    // future: Filter, GenericClosure, Sort, All, Any, ConcatMap, ...
+}
+
+impl<'gc> BuiltinState<'gc> {
+    pub(super) fn resume(
+        self,
+        val: StrictValue<'gc>,
+        ctx: &PrimOpCtx<'_, 'gc>,
+    ) -> BuiltinResult<'gc> {
+        match self {
+            BuiltinState::FoldlStrict(s) => s.resume(val, ctx),
+        }
+    }
+}
+
+pub(super) struct PrimOpCtx<'a, 'gc> {
+    pub(super) vm: &'a VM<'gc>,
+    pub(super) mc: &'a Mutation<'gc>,
+    pub(super) strings: &'a DefaultStringInterner,
+}
+
+macro_rules! force_inline_or_err {
+    ($ctx:expr, $val:expr) => {{
+        let val = $val;
+        match $ctx.vm.force_inline(val) {
+            Ok(ForceResult::Ready(v)) => v,
+            Ok(_) => {
+                return BuiltinResult::Error(VM::err(
+                    "value requires evaluation in non-stateful builtin context",
+                ));
+            }
+            Err(e) => return BuiltinResult::Error(e),
+        }
+    }};
+}
+
+macro_rules! force {
+    ($ctx:expr, $state:expr, $val:expr) => {{
+        let val = $val;
+        match $ctx.vm.force_inline(val) {
+            Ok(ForceResult::Ready(v)) => v,
+            Ok(ForceResult::NeedEval { .. } | ForceResult::NeedApply(_)) => {
+                return BuiltinResult::Force($state, val);
+            }
+            Err(e) => return BuiltinResult::Error(e),
+        }
+    }};
+}
+
+macro_rules! call {
+    ($ctx:expr, $state:expr, $func:expr, $arg:expr) => {{
+        let func = $func;
+        let arg = $arg;
+        return BuiltinResult::Call($state, func, arg);
+    }};
+}
+
+macro_rules! call_and_force {
+    ($ctx:expr, $state:expr, $func:expr, $arg:expr) => {{
+        let func = $func;
+        let arg = $arg;
+        return BuiltinResult::CallAndForce($state, func, arg);
+    }};
+}
+
+pub(super) fn dispatch_strict_builtin<'gc>(
+    id: BuiltinId,
+    args: PrimOpStrictArgs<'gc>,
+    _arity: u8,
+    ctx: &PrimOpCtx<'_, 'gc>,
+) -> BuiltinResult<'gc> {
+    match id {
+        BuiltinId::TypeOf => {
+            let val = args[0];
+            let name = if val.as_inline::<i32>().is_some() || val.as_gc::<i64>().is_some() {
+                "int"
+            } else if val.as_float().is_some() {
+                "float"
+            } else if val.as_inline::<bool>().is_some() {
+                "bool"
+            } else if VM::get_string(val, ctx.strings).is_some() {
+                "string"
+            } else if val.is::<Null>() {
+                "null"
+            } else if val.as_gc::<AttrSet<'gc>>().is_some() {
+                "set"
+            } else if val.as_gc::<List<'gc>>().is_some() {
+                "list"
+            } else if val.as_gc::<Closure<'gc>>().is_some()
+                || val.as_inline::<PrimOp>().is_some()
+                || val.as_gc::<PrimOpApp<'gc>>().is_some()
+            {
+                "lambda"
+            } else {
+                return BuiltinResult::Error(VM::err("typeOf: unknown type"));
+            };
+            let sid = ctx.strings.get(name).expect("typeOf string not interned");
+            BuiltinResult::Done(Value::new_inline(StringId(sid)))
+        }
+
+        BuiltinId::IsNull => BuiltinResult::Done(Value::new_inline(args[0].is::<Null>())),
+        BuiltinId::IsAttrs => {
+            BuiltinResult::Done(Value::new_inline(args[0].as_gc::<AttrSet<'gc>>().is_some()))
+        }
+        BuiltinId::IsBool => {
+            BuiltinResult::Done(Value::new_inline(args[0].as_inline::<bool>().is_some()))
+        }
+        BuiltinId::IsFloat => BuiltinResult::Done(Value::new_inline(args[0].as_float().is_some())),
+        BuiltinId::IsFunction => {
+            let v = args[0];
+            let is_func = v.as_gc::<Closure<'gc>>().is_some()
+                || v.as_inline::<PrimOp>().is_some()
+                || v.as_gc::<PrimOpApp<'gc>>().is_some();
+            BuiltinResult::Done(Value::new_inline(is_func))
+        }
+        BuiltinId::IsInt => {
+            let v = args[0];
+            let is_int = v.as_inline::<i32>().is_some() || v.as_gc::<i64>().is_some();
+            BuiltinResult::Done(Value::new_inline(is_int))
+        }
+        BuiltinId::IsList => {
+            BuiltinResult::Done(Value::new_inline(args[0].as_gc::<List<'gc>>().is_some()))
+        }
+        BuiltinId::IsString => {
+            let v = args[0];
+            let is_str = v.as_inline::<StringId>().is_some() || v.as_gc::<NixString>().is_some();
+            BuiltinResult::Done(Value::new_inline(is_str))
+        }
+        BuiltinId::IsPath => BuiltinResult::Done(Value::new_inline(false)),
+
+        BuiltinId::Length => {
+            let Some(list) = args[0].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.length: not a list"));
+            };
+            BuiltinResult::Done(VM::make_int(list.inner.len() as i64, ctx.mc))
+        }
+        BuiltinId::Head => {
+            let Some(list) = args[0].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.head: not a list"));
+            };
+            if list.inner.is_empty() {
+                return BuiltinResult::Error(VM::err("builtins.head: empty list"));
+            }
+            BuiltinResult::Done(list.inner[0])
+        }
+        BuiltinId::Tail => {
+            let Some(list) = args[0].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.tail: not a list"));
+            };
+            if list.inner.is_empty() {
+                return BuiltinResult::Error(VM::err("builtins.tail: empty list"));
+            }
+            let tail = List {
+                inner: SmallVec::from_slice(&list.inner[1..]),
+            };
+            BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, tail)))
+        }
+
+        BuiltinId::AttrNames => {
+            let Some(attrs) = args[0].as_gc::<AttrSet<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.attrNames: not a set"));
+            };
+            let items: SmallVec<[Value<'gc>; 4]> =
+                attrs.iter().map(|(k, _)| Value::new_inline(*k)).collect();
+            BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, List { inner: items })))
+        }
+        BuiltinId::AttrValues => {
+            let Some(attrs) = args[0].as_gc::<AttrSet<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.attrValues: not a set"));
+            };
+            let items: SmallVec<[Value<'gc>; 4]> = attrs.iter().map(|(_, v)| *v).collect();
+            BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, List { inner: items })))
+        }
+
+        BuiltinId::Map => {
+            let f = args[0];
+            let Some(list) = args[1].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.map: second argument is not a list",
+                ));
+            };
+            if list.inner.is_empty() {
+                return BuiltinResult::Done(Value::new_gc(Gc::new(
+                    ctx.mc,
+                    List {
+                        inner: SmallVec::new(),
+                    },
+                )));
+            }
+            let new_elems: SmallVec<[Value<'gc>; 4]> = list
+                .inner
+                .iter()
+                .map(|elem| {
+                    let thunk: Gc<'gc, Thunk<'gc>> = Gc::new(
+                        ctx.mc,
+                        RefLock::new(ThunkState::Apply {
+                            func: f.relax(),
+                            arg: *elem,
+                        }),
+                    );
+                    Value::new_gc(thunk)
+                })
+                .collect();
+            BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, List { inner: new_elems })))
+        }
+
+        BuiltinId::GenList => {
+            let f = args[0];
+            let len_val = args[1];
+            let Some(len) = VM::as_num(len_val) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.genList: second argument is not a number",
+                ));
+            };
+            let super::vm::NixNum::Int(len) = len else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.genList: second argument is not an integer",
+                ));
+            };
+            if len < 0 {
+                return BuiltinResult::Error(VM::err("builtins.genList: negative length"));
+            }
+            let items: SmallVec<[Value<'gc>; 4]> = (0..len)
+                .map(|i| {
+                    let arg = VM::make_int(i, ctx.mc);
+                    let thunk: Gc<'gc, Thunk<'gc>> = Gc::new(
+                        ctx.mc,
+                        RefLock::new(ThunkState::Apply {
+                            func: f.relax(),
+                            arg,
+                        }),
+                    );
+                    Value::new_gc(thunk)
+                })
+                .collect();
+            BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, List { inner: items })))
+        }
+
+        BuiltinId::ElemAt => {
+            let Some(list) = args[0].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.elemAt: not a list"));
+            };
+            let Some(idx) = VM::as_num(args[1]) else {
+                return BuiltinResult::Error(VM::err("builtins.elemAt: index is not a number"));
+            };
+            let super::vm::NixNum::Int(idx) = idx else {
+                return BuiltinResult::Error(VM::err("builtins.elemAt: index is not an integer"));
+            };
+            if idx < 0 || idx as usize >= list.inner.len() {
+                return BuiltinResult::Error(VM::err(format!(
+                    "builtins.elemAt: index {} out of bounds for list of length {}",
+                    idx,
+                    list.inner.len()
+                )));
+            }
+            BuiltinResult::Done(list.inner[idx as usize])
+        }
+
+        BuiltinId::GetAttr => {
+            let Some(name) = VM::get_string(args[0], ctx.strings) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.getAttr: first argument is not a string",
+                ));
+            };
+            let Some(sid) = ctx.strings.get(name) else {
+                return BuiltinResult::Error(VM::err(format!(
+                    "builtins.getAttr: attribute '{}' not found",
+                    name
+                )));
+            };
+            let Some(attrs) = args[1].as_gc::<AttrSet<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.getAttr: second argument is not a set",
+                ));
+            };
+            match attrs.lookup(StringId(sid)) {
+                Some(v) => BuiltinResult::Done(v),
+                None => BuiltinResult::Error(VM::err(format!("attribute '{}' missing", name))),
+            }
+        }
+
+        BuiltinId::HasAttr => {
+            let Some(name) = VM::get_string(args[0], ctx.strings) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.hasAttr: first argument is not a string",
+                ));
+            };
+            let Some(attrs) = args[1].as_gc::<AttrSet<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.hasAttr: second argument is not a set",
+                ));
+            };
+            let has = ctx
+                .strings
+                .get(name)
+                .map(|sid| attrs.has(StringId(sid)))
+                .unwrap_or(false);
+            BuiltinResult::Done(Value::new_inline(has))
+        }
+
+        BuiltinId::RemoveAttrs => {
+            let Some(attrs) = args[0].as_gc::<AttrSet<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.removeAttrs: first argument is not a set",
+                ));
+            };
+            let Some(remove_list) = args[1].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.removeAttrs: second argument is not a list",
+                ));
+            };
+            let mut to_remove = Vec::new();
+            for item in remove_list.inner.iter() {
+                let sv = force_inline_or_err!(ctx, *item);
+                if let Some(s) = VM::get_string(sv, ctx.strings)
+                    && let Some(sid) = ctx.strings.get(s)
+                {
+                    to_remove.push(StringId(sid));
+                }
+            }
+            let entries: SmallVec<[(StringId, Value<'gc>); 4]> = attrs
+                .iter()
+                .filter(|(k, _)| !to_remove.contains(k))
+                .cloned()
+                .collect();
+            let new_attrs = Gc::new(ctx.mc, unsafe { AttrSet::from_sorted_unchecked(entries) });
+            BuiltinResult::Done(Value::new_gc(new_attrs))
+        }
+
+        BuiltinId::IntersectAttrs => {
+            let Some(a) = args[0].as_gc::<AttrSet<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.intersectAttrs: first argument is not a set",
+                ));
+            };
+            let Some(b) = args[1].as_gc::<AttrSet<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.intersectAttrs: second argument is not a set",
+                ));
+            };
+            let entries: SmallVec<[(StringId, Value<'gc>); 4]> =
+                b.iter().filter(|(k, _)| a.has(*k)).cloned().collect();
+            let new_attrs = Gc::new(ctx.mc, unsafe { AttrSet::from_sorted_unchecked(entries) });
+            BuiltinResult::Done(Value::new_gc(new_attrs))
+        }
+
+        BuiltinId::ListToAttrs => {
+            let Some(list) = args[0].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.listToAttrs: not a list"));
+            };
+            let name_sid = ctx.strings.get("name").expect("'name' not interned");
+            let value_sid = ctx.strings.get("value").expect("'value' not interned");
+            let mut entries = SmallVec::<[(StringId, Value<'gc>); 4]>::new();
+            for item in list.inner.iter() {
+                let sv = force_inline_or_err!(ctx, *item);
+                let Some(attr_set) = sv.as_gc::<AttrSet<'gc>>() else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.listToAttrs: element is not a set",
+                    ));
+                };
+                let Some(name_val) = attr_set.lookup(StringId(name_sid)) else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.listToAttrs: element missing 'name'",
+                    ));
+                };
+                let name_sv = force_inline_or_err!(ctx, name_val);
+                let Some(name_str) = VM::get_string(name_sv, ctx.strings) else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.listToAttrs: 'name' is not a string",
+                    ));
+                };
+                let Some(value_val) = attr_set.lookup(StringId(value_sid)) else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.listToAttrs: element missing 'value'",
+                    ));
+                };
+                let Some(key_sym) = ctx.strings.get(name_str) else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.listToAttrs: name not interned",
+                    ));
+                };
+                entries.push((StringId(key_sym), value_val));
+            }
+            entries.sort_by_key(|(k, _)| *k);
+            entries.dedup_by_key(|(k, _)| *k);
+            let new_attrs = Gc::new(ctx.mc, unsafe { AttrSet::from_sorted_unchecked(entries) });
+            BuiltinResult::Done(Value::new_gc(new_attrs))
+        }
+
+        BuiltinId::ConcatLists => {
+            let Some(list) = args[0].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err("builtins.concatLists: not a list"));
+            };
+            let mut result = SmallVec::<[Value<'gc>; 4]>::new();
+            for item in list.inner.iter() {
+                let sv = force_inline_or_err!(ctx, *item);
+                let Some(inner) = sv.as_gc::<List<'gc>>() else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.concatLists: element is not a list",
+                    ));
+                };
+                result.extend(inner.inner.iter().cloned());
+            }
+            BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, List { inner: result })))
+        }
+
+        BuiltinId::LessThan => {
+            match ctx
+                .vm
+                .compare_values(args[0], args[1], ctx.strings, |o| o.is_lt())
+            {
+                Ok(v) => BuiltinResult::Done(v),
+                Err(e) => BuiltinResult::Error(e),
+            }
+        }
+
+        BuiltinId::Add => {
+            match ctx.vm.compute_binop(
+                super::vm::BinOpTag::Add,
+                args[0],
+                args[1],
+                ctx.mc,
+                ctx.strings,
+            ) {
+                Ok(v) => BuiltinResult::Done(v),
+                Err(e) => BuiltinResult::Error(e),
+            }
+        }
+        BuiltinId::Sub => {
+            match ctx
+                .vm
+                .numeric_binop(args[0], args[1], ctx.mc, i64::wrapping_sub, |a, b| a - b)
+            {
+                Ok(v) => BuiltinResult::Done(v),
+                Err(e) => BuiltinResult::Error(e),
+            }
+        }
+        BuiltinId::Mul => {
+            match ctx
+                .vm
+                .numeric_binop(args[0], args[1], ctx.mc, i64::wrapping_mul, |a, b| a * b)
+            {
+                Ok(v) => BuiltinResult::Done(v),
+                Err(e) => BuiltinResult::Error(e),
+            }
+        }
+        BuiltinId::Div => {
+            match ctx.vm.compute_binop(
+                super::vm::BinOpTag::Div,
+                args[0],
+                args[1],
+                ctx.mc,
+                ctx.strings,
+            ) {
+                Ok(v) => BuiltinResult::Done(v),
+                Err(e) => BuiltinResult::Error(e),
+            }
+        }
+
+        BuiltinId::BitAnd => {
+            let (Some(super::vm::NixNum::Int(a)), Some(super::vm::NixNum::Int(b))) =
+                (VM::as_num(args[0]), VM::as_num(args[1]))
+            else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.bitAnd: arguments must be integers",
+                ));
+            };
+            BuiltinResult::Done(VM::make_int(a & b, ctx.mc))
+        }
+        BuiltinId::BitOr => {
+            let (Some(super::vm::NixNum::Int(a)), Some(super::vm::NixNum::Int(b))) =
+                (VM::as_num(args[0]), VM::as_num(args[1]))
+            else {
+                return BuiltinResult::Error(VM::err("builtins.bitOr: arguments must be integers"));
+            };
+            BuiltinResult::Done(VM::make_int(a | b, ctx.mc))
+        }
+        BuiltinId::BitXor => {
+            let (Some(super::vm::NixNum::Int(a)), Some(super::vm::NixNum::Int(b))) =
+                (VM::as_num(args[0]), VM::as_num(args[1]))
+            else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.bitXor: arguments must be integers",
+                ));
+            };
+            BuiltinResult::Done(VM::make_int(a ^ b, ctx.mc))
+        }
+
+        BuiltinId::Ceil => {
+            if let Some(f) = args[0].as_float() {
+                BuiltinResult::Done(VM::make_int(f.ceil() as i64, ctx.mc))
+            } else if VM::as_num(args[0]).is_some() {
+                BuiltinResult::Done(args[0].relax())
+            } else {
+                BuiltinResult::Error(VM::err("builtins.ceil: not a number"))
+            }
+        }
+        BuiltinId::Floor => {
+            if let Some(f) = args[0].as_float() {
+                BuiltinResult::Done(VM::make_int(f.floor() as i64, ctx.mc))
+            } else if VM::as_num(args[0]).is_some() {
+                BuiltinResult::Done(args[0].relax())
+            } else {
+                BuiltinResult::Error(VM::err("builtins.floor: not a number"))
+            }
+        }
+
+        BuiltinId::StringLength => {
+            let Some(s) = VM::get_string(args[0], ctx.strings) else {
+                return BuiltinResult::Error(VM::err("builtins.stringLength: not a string"));
+            };
+            BuiltinResult::Done(VM::make_int(s.len() as i64, ctx.mc))
+        }
+
+        BuiltinId::Substring => {
+            let Some(super::vm::NixNum::Int(start)) = VM::as_num(args[0]) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.substring: start is not an integer",
+                ));
+            };
+            let Some(super::vm::NixNum::Int(len)) = VM::as_num(args[1]) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.substring: length is not an integer",
+                ));
+            };
+            let Some(s) = VM::get_string(args[2], ctx.strings) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.substring: third argument is not a string",
+                ));
+            };
+            let start = start.max(0) as usize;
+            if start >= s.len() {
+                let ns = Gc::new(ctx.mc, NixString::new(""));
+                return BuiltinResult::Done(Value::new_gc(ns));
+            }
+            let end = if len < 0 {
+                s.len()
+            } else {
+                (start + len as usize).min(s.len())
+            };
+            let result = &s[start..end];
+            let ns = Gc::new(ctx.mc, NixString::new(result));
+            BuiltinResult::Done(Value::new_gc(ns))
+        }
+
+        BuiltinId::ToString => {
+            let v = args[0];
+            if let Some(s) = VM::get_string(v, ctx.strings) {
+                let ns = Gc::new(ctx.mc, NixString::new(s));
+                BuiltinResult::Done(Value::new_gc(ns))
+            } else if let Some(b) = v.as_inline::<bool>() {
+                let s = if b { "1" } else { "" };
+                let ns = Gc::new(ctx.mc, NixString::new(s));
+                BuiltinResult::Done(Value::new_gc(ns))
+            } else if v.is::<Null>() {
+                let ns = Gc::new(ctx.mc, NixString::new(""));
+                BuiltinResult::Done(Value::new_gc(ns))
+            } else if let Some(n) = VM::as_num(v) {
+                let s = match n {
+                    super::vm::NixNum::Int(i) => i.to_string(),
+                    super::vm::NixNum::Float(f) => format!("{f}"),
+                };
+                let ns = Gc::new(ctx.mc, NixString::new(s));
+                BuiltinResult::Done(Value::new_gc(ns))
+            } else {
+                BuiltinResult::Error(VM::err("builtins.toString: cannot coerce to string"))
+            }
+        }
+
+        BuiltinId::Abort => {
+            let Some(msg) = VM::get_string(args[0], ctx.strings) else {
+                return BuiltinResult::Error(VM::err("builtins.abort: argument is not a string"));
+            };
+            BuiltinResult::Error(VmError::Uncatchable(crate::error::Error::eval_error(
+                format!("evaluation aborted with the following error message: '{msg}'"),
+            )))
+        }
+
+        BuiltinId::Throw => {
+            let Some(msg) = VM::get_string(args[0], ctx.strings) else {
+                return BuiltinResult::Error(VM::err("builtins.throw: argument is not a string"));
+            };
+            BuiltinResult::Error(VmError::Catchable(msg.to_owned()))
+        }
+
+        BuiltinId::FunctionArgs => {
+            let v = args[0];
+            if let Some(closure) = v.as_gc::<Closure<'gc>>() {
+                if let Some(ref pattern) = closure.pattern {
+                    let mut entries = SmallVec::<[(StringId, Value<'gc>); 4]>::new();
+                    for &name in &pattern.required {
+                        entries.push((name, Value::new_inline(false)));
+                    }
+                    for &name in &pattern.optional {
+                        entries.push((name, Value::new_inline(true)));
+                    }
+                    entries.sort_by_key(|(k, _)| *k);
+                    let attrs = Gc::new(ctx.mc, unsafe { AttrSet::from_sorted_unchecked(entries) });
+                    BuiltinResult::Done(Value::new_gc(attrs))
+                } else {
+                    BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, AttrSet::default())))
+                }
+            } else {
+                BuiltinResult::Done(Value::new_gc(Gc::new(ctx.mc, AttrSet::default())))
+            }
+        }
+
+        BuiltinId::FoldlStrict => FoldlStrict::call(args, ctx),
+
+        BuiltinId::Elem => {
+            let Some(list) = args[1].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.elem: second argument is not a list",
+                ));
+            };
+            let needle = args[0];
+            for item in list.inner.iter() {
+                let sv = force_inline_or_err!(ctx, *item);
+                if ctx.vm.values_equal(needle, sv, ctx.strings) {
+                    return BuiltinResult::Done(Value::new_inline(true));
+                }
+            }
+            BuiltinResult::Done(Value::new_inline(false))
+        }
+
+        BuiltinId::ReplaceStrings => {
+            let Some(from_list) = args[0].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.replaceStrings: first argument is not a list",
+                ));
+            };
+            let Some(to_list) = args[1].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.replaceStrings: second argument is not a list",
+                ));
+            };
+            let Some(s) = VM::get_string(args[2], ctx.strings) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.replaceStrings: third argument is not a string",
+                ));
+            };
+            if from_list.inner.len() != to_list.inner.len() {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.replaceStrings: lists must have same length",
+                ));
+            }
+
+            let mut from_strs = Vec::new();
+            let mut to_strs = Vec::new();
+            for (f, t) in from_list.inner.iter().zip(to_list.inner.iter()) {
+                let fv = force_inline_or_err!(ctx, *f);
+                let tv = force_inline_or_err!(ctx, *t);
+                let Some(fs) = VM::get_string(fv, ctx.strings) else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.replaceStrings: from element is not a string",
+                    ));
+                };
+                let Some(ts) = VM::get_string(tv, ctx.strings) else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.replaceStrings: to element is not a string",
+                    ));
+                };
+                from_strs.push(fs.to_owned());
+                to_strs.push(ts.to_owned());
+            }
+
+            let s = s.to_owned();
+            let mut result = String::new();
+            let mut i = 0;
+            while i < s.len() {
+                let mut found = false;
+                for (j, from) in from_strs.iter().enumerate() {
+                    if from.is_empty() {
+                        result.push_str(&to_strs[j]);
+                        result.push(s.as_bytes()[i] as char);
+                        i += 1;
+                        found = true;
+                        break;
+                    }
+                    if s[i..].starts_with(from.as_str()) {
+                        result.push_str(&to_strs[j]);
+                        i += from.len();
+                        found = true;
+                        break;
+                    }
+                }
+                if !found {
+                    result.push(s.as_bytes()[i] as char);
+                    i += 1;
+                }
+            }
+            if from_strs.iter().any(|f| f.is_empty()) {
+                let j = from_strs
+                    .iter()
+                    .position(|f| f.is_empty())
+                    .expect("just checked");
+                result.push_str(&to_strs[j]);
+            }
+
+            let ns = Gc::new(ctx.mc, NixString::new(result));
+            BuiltinResult::Done(Value::new_gc(ns))
+        }
+
+        BuiltinId::ConcatStringsSep => {
+            let Some(sep) = VM::get_string(args[0], ctx.strings) else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.concatStringsSep: first argument is not a string",
+                ));
+            };
+            let sep = sep.to_owned();
+            let Some(list) = args[1].as_gc::<List<'gc>>() else {
+                return BuiltinResult::Error(VM::err(
+                    "builtins.concatStringsSep: second argument is not a list",
+                ));
+            };
+            let mut result = String::new();
+            for (i, item) in list.inner.iter().enumerate() {
+                if i > 0 {
+                    result.push_str(&sep);
+                }
+                let sv = force_inline_or_err!(ctx, *item);
+                let Some(s) = VM::get_string(sv, ctx.strings) else {
+                    return BuiltinResult::Error(VM::err(
+                        "builtins.concatStringsSep: element is not a string",
+                    ));
+                };
+                result.push_str(s);
+            }
+            let ns = Gc::new(ctx.mc, NixString::new(result));
+            BuiltinResult::Done(Value::new_gc(ns))
+        }
+
+        BuiltinId::FromJSON => {
+            let Some(s) = VM::get_string(args[0], ctx.strings) else {
+                return BuiltinResult::Error(VM::err("builtins.fromJSON: not a string"));
+            };
+            match serde_json::from_str::<serde_json::Value>(s) {
+                Ok(json) => {
+                    let v = json_to_nix(&json, ctx.mc, ctx.strings);
+                    BuiltinResult::Done(v)
+                }
+                Err(e) => BuiltinResult::Error(VM::err(format!("builtins.fromJSON: {e}"))),
+            }
+        }
+
+        BuiltinId::ToJSON => BuiltinResult::Error(VM::err("builtins.toJSON: not yet implemented")),
+
+        BuiltinId::Null => BuiltinResult::Done(Value::new_inline(Null)),
+
+        _ => BuiltinResult::Error(VM::err(format!("builtin {:?} not yet implemented", id))),
+    }
+}
+
+pub(super) fn dispatch_lazy_builtin<'gc>(
+    id: BuiltinId,
+    args: &PrimOpArgs<'gc>,
+    _arity: u8,
+    ctx: &PrimOpCtx<'_, 'gc>,
+) -> BuiltinResult<'gc> {
+    match id {
+        BuiltinId::Seq => {
+            let _ = force_inline_or_err!(ctx, args[0]);
+            BuiltinResult::Done(args[1])
+        }
+        BuiltinId::DeepSeq => {
+            // TODO: deep force
+            let _ = force_inline_or_err!(ctx, args[0]);
+            BuiltinResult::Done(args[1])
+        }
+        BuiltinId::Trace => {
+            let sv = force_inline_or_err!(ctx, args[0]);
+            if let Some(s) = VM::get_string(sv, ctx.strings) {
+                eprintln!("trace: {s}");
+            } else {
+                eprintln!("trace: <non-string>");
+            }
+            BuiltinResult::Done(args[1])
+        }
+        BuiltinId::Warn => {
+            let sv = force_inline_or_err!(ctx, args[0]);
+            if let Some(s) = VM::get_string(sv, ctx.strings) {
+                eprintln!("warning: {s}");
+            } else {
+                eprintln!("warning: <non-string>");
+            }
+            BuiltinResult::Done(args[1])
+        }
+        BuiltinId::TryEval => BuiltinResult::Error(VM::err(
+            "builtins.tryEval: requires catch frame support (TODO)",
+        )),
+        BuiltinId::AddErrorContext => BuiltinResult::Done(args[1]),
+        BuiltinId::Break => BuiltinResult::Done(args[0]),
+        _ => BuiltinResult::Error(VM::err(format!(
+            "lazy builtin {:?} not yet implemented",
+            id
+        ))),
+    }
+}
+
+fn json_to_nix<'gc>(
+    json: &serde_json::Value,
+    mc: &Mutation<'gc>,
+    strings: &DefaultStringInterner,
+) -> Value<'gc> {
+    match json {
+        serde_json::Value::Null => Value::new_inline(Null),
+        serde_json::Value::Bool(b) => Value::new_inline(*b),
+        serde_json::Value::Number(n) => {
+            if let Some(i) = n.as_i64() {
+                VM::make_int(i, mc)
+            } else if let Some(f) = n.as_f64() {
+                Value::new_float(f)
+            } else {
+                Value::new_inline(Null)
+            }
+        }
+        serde_json::Value::String(s) => {
+            let ns = Gc::new(mc, NixString::new(s.as_str()));
+            Value::new_gc(ns)
+        }
+        serde_json::Value::Array(arr) => {
+            let items: SmallVec<[Value<'gc>; 4]> =
+                arr.iter().map(|v| json_to_nix(v, mc, strings)).collect();
+            Value::new_gc(Gc::new(mc, List { inner: items }))
+        }
+        serde_json::Value::Object(obj) => {
+            let mut entries = SmallVec::<[(StringId, Value<'gc>); 4]>::new();
+            for (k, v) in obj {
+                if let Some(sym) = strings.get(k.as_str()) {
+                    entries.push((StringId(sym), json_to_nix(v, mc, strings)));
+                }
+            }
+            entries.sort_by_key(|(k, _)| *k);
+            let attrs = Gc::new(mc, unsafe { AttrSet::from_sorted_unchecked(entries) });
+            Value::new_gc(attrs)
+        }
+    }
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub(super) struct FoldlStrict<'gc> {
+    op: StrictValue<'gc>,
+    list: Gc<'gc, List<'gc>>,
+    acc: StrictValue<'gc>,
+    index: usize,
+    phase: FoldlPhase<'gc>,
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+enum FoldlPhase<'gc> {
+    CallOp,
+    CallPartial(StrictValue<'gc>),
+}
+
+impl<'gc> FoldlStrict<'gc> {
+    fn call(args: PrimOpStrictArgs<'gc>, ctx: &PrimOpCtx<'_, 'gc>) -> BuiltinResult<'gc> {
+        let op = args[0];
+        let nul = args[1];
+        let Some(list) = args[2].as_gc::<List<'gc>>() else {
+            return BuiltinResult::Error(VM::err("builtins.foldl': third argument is not a list"));
+        };
+        if list.inner.is_empty() {
+            return BuiltinResult::Done(nul.relax());
+        }
+        let state = FoldlStrict {
+            op,
+            list,
+            acc: nul,
+            index: 0,
+            phase: FoldlPhase::CallOp,
+        };
+        state.step(ctx)
+    }
+
+    fn step(self, _ctx: &PrimOpCtx<'_, 'gc>) -> BuiltinResult<'gc> {
+        let state = BuiltinState::FoldlStrict(FoldlStrict {
+            op: self.op,
+            list: self.list,
+            acc: self.acc,
+            index: self.index,
+            phase: FoldlPhase::CallOp,
+        });
+        call!(ctx, state, self.op, self.acc.relax())
+    }
+
+    fn resume(mut self, val: StrictValue<'gc>, ctx: &PrimOpCtx<'_, 'gc>) -> BuiltinResult<'gc> {
+        match self.phase {
+            FoldlPhase::CallOp => {
+                let partial = val;
+                let elem = self.list.inner[self.index];
+                self.phase = FoldlPhase::CallPartial(partial);
+                let state = BuiltinState::FoldlStrict(self);
+                call_and_force!(ctx, state, partial, elem)
+            }
+            FoldlPhase::CallPartial(_) => {
+                self.acc = val;
+                self.index += 1;
+                self.phase = FoldlPhase::CallOp;
+                if self.index >= self.list.inner.len() {
+                    return BuiltinResult::Done(self.acc.relax());
+                }
+                self.step(ctx)
+            }
+        }
+    }
+}

fix/src/runtime/stack.rs

@@ -3,14 +3,13 @@ use std::mem::MaybeUninit;
 use gc_arena::Collect;
 use smallvec::SmallVec;
 
-// FIXME: Drop???
 pub(super) struct Stack<const N: usize, T> {
     inner: Box<[MaybeUninit<T>; N]>,
     len: usize,
 }
 
 unsafe impl<'gc, const N: usize, T: Collect<'gc> + 'gc> Collect<'gc> for Stack<N, T> {
-    const NEEDS_TRACE: bool = true;
+    const NEEDS_TRACE: bool = T::NEEDS_TRACE;
     fn trace<U: gc_arena::collect::Trace<'gc>>(&self, cc: &mut U) {
         for item in self.inner[..self.len].iter() {
             unsafe {
@@ -34,6 +33,13 @@ impl<const N: usize, T> Stack<N, T> {
         }
     }
 
+    pub(super) unsafe fn push_unchecked(&mut self, val: T) {
+        unsafe {
+            self.inner.get_unchecked_mut(self.len).write(val);
+        }
+        self.len += 1;
+    }
+
     pub(super) fn push(&mut self, val: T) -> Result<(), T> {
         if self.len == N {
             return Err(val);

fix/src/runtime/value.rs

@@ -3,16 +3,19 @@ use std::marker::PhantomData;
 use std::mem::size_of;
 use std::ops::Deref;
 
-use boxing::nan::raw::{RawBox, RawStore, RawTag, Value as RawValue};
 use gc_arena::{Collect, Gc, Mutation, RefLock, collect::Trace};
+use num_enum::TryFromPrimitive;
 use sealed::sealed;
 use smallvec::SmallVec;
 use string_interner::{Symbol, symbol::SymbolU32};
 
-use crate::ir::StringId;
+use crate::boxing::{RawBox, RawStore, RawTag, Value as RawValue};
+use crate::{ir::StringId, runtime::builtins::BuiltinId};
 
 #[sealed]
-pub(crate) trait Storable {
+/// # Safety
+/// TAG must be unique among all implementors.
+pub(crate) unsafe trait Storable {
     const TAG: (bool, u8);
 }
 pub(crate) trait InlineStorable: Storable + RawStore {}
@@ -25,14 +28,14 @@ macro_rules! define_value_types {
     ) => {
         $(
         #[sealed]
-        impl Storable for $itype {
+        unsafe impl Storable for $itype {
             const TAG: (bool, u8) = $itag;
         }
         impl InlineStorable for $itype {}
         )*
         $(
         #[sealed]
-        impl Storable for $gtype {
+        unsafe impl Storable for $gtype {
             const TAG: (bool, u8) = $gtag;
         }
         impl GcStorable for $gtype {}
@@ -116,22 +119,13 @@ define_value_types! {
 /// # Nix runtime value representation
 ///
 /// NaN-boxed value fitting in 8 bytes.
+#[derive(Copy, Clone)]
 #[repr(transparent)]
 pub(crate) struct Value<'gc> {
     raw: RawBox,
     _marker: PhantomData<Gc<'gc, ()>>,
 }
 
-impl Clone for Value<'_> {
-    #[inline]
-    fn clone(&self) -> Self {
-        Self {
-            raw: self.raw.clone(),
-            _marker: PhantomData,
-        }
-    }
-}
-
 impl Default for Value<'_> {
     #[inline(always)]
     fn default() -> Self {
@@ -291,14 +285,23 @@ impl fmt::Debug for NixString {
     }
 }
 
-#[derive(Collect, Debug)]
+#[derive(Collect, Debug, Default)]
 #[collect(no_drop)]
 pub(crate) struct AttrSet<'gc> {
-    pub(crate) entries: SmallVec<[(StringId, Value<'gc>); 4]>,
+    entries: SmallVec<[(StringId, Value<'gc>); 4]>,
+}
+
+impl<'gc> Deref for AttrSet<'gc> {
+    type Target = [(StringId, Value<'gc>)];
+    fn deref(&self) -> &Self::Target {
+        &self.entries
+    }
 }
 
 impl<'gc> AttrSet<'gc> {
-    pub(crate) fn from_sorted(entries: SmallVec<[(StringId, Value<'gc>); 4]>) -> Self {
+    pub(crate) unsafe fn from_sorted_unchecked(
+        entries: SmallVec<[(StringId, Value<'gc>); 4]>,
+    ) -> Self {
         debug_assert!(entries.is_sorted_by_key(|(key, _)| *key));
         Self { entries }
     }
@@ -307,13 +310,11 @@ impl<'gc> AttrSet<'gc> {
         self.entries
             .binary_search_by_key(&key, |(k, _)| *k)
             .ok()
-            .map(|i| self.entries[i].1.clone())
+            .map(|i| self.entries[i].1)
     }
 
     pub(crate) fn has(&self, key: StringId) -> bool {
-        self.entries
-            .binary_search_by_key(&key, |(k, _)| *k)
-            .is_ok()
+        self.entries.binary_search_by_key(&key, |(k, _)| *k).is_ok()
     }
 
     pub(crate) fn merge(&self, other: &Self, mc: &Mutation<'gc>) -> Gc<'gc, Self> {
@@ -328,15 +329,15 @@ impl<'gc> AttrSet<'gc> {
         while i < self.entries.len() && j < other.entries.len() {
             match self.entries[i].0.cmp(&other.entries[j].0) {
                 Less => {
-                    entries.push(self.entries[i].clone());
+                    entries.push(self.entries[i]);
                     i += 1;
                 }
                 Greater => {
-                    entries.push(other.entries[j].clone());
+                    entries.push(other.entries[j]);
                     j += 1;
                 }
                 Equal => {
-                    entries.push(other.entries[j].clone());
+                    entries.push(other.entries[j]);
                     i += 1;
                     j += 1;
                 }
@@ -351,7 +352,7 @@ impl<'gc> AttrSet<'gc> {
     }
 }
 
-#[derive(Collect, Debug)]
+#[derive(Collect, Debug, Default)]
 #[collect(no_drop)]
 pub(crate) struct List<'gc> {
     pub(crate) inner: SmallVec<[Value<'gc>; 4]>,
@@ -366,6 +367,10 @@ pub(crate) enum ThunkState<'gc> {
         ip: u32,
         env: Gc<'gc, RefLock<Env<'gc>>>,
     },
+    Apply {
+        func: Value<'gc>,
+        arg: Value<'gc>,
+    },
     Blackhole,
     Evaluated(Value<'gc>),
 }
@@ -420,17 +425,20 @@ pub(crate) struct PatternInfo {
 #[derive(Clone, Copy, Debug, Collect)]
 #[collect(require_static)]
 pub(crate) struct PrimOp {
-    pub(crate) id: u8,
+    pub(crate) id: BuiltinId,
     pub(crate) arity: u8,
 }
 
 impl RawStore for PrimOp {
     fn to_val(self, value: &mut RawValue) {
-        value.set_data([0, 0, 0, 0, self.id, self.arity]);
+        value.set_data([0, 0, 0, 0, self.id as u8, self.arity]);
     }
     fn from_val(value: &RawValue) -> Self {
         let [.., id, arity] = *value.data();
-        Self { id, arity }
+        Self {
+            id: BuiltinId::try_from_primitive(id).expect("invalid BuiltinId"),
+            arity,
+        }
     }
 }
 
@@ -441,6 +449,7 @@ pub(crate) struct PrimOpApp<'gc> {
     pub(crate) args: SmallVec<[Value<'gc>; 2]>,
 }
 
+#[derive(Copy, Clone, Default)]
 #[repr(transparent)]
 pub(crate) struct StrictValue<'gc>(Value<'gc>);
 
@@ -455,7 +464,7 @@ impl<'gc> StrictValue<'gc> {
     }
 
     #[inline]
-    pub(crate) fn into_relaxed(self) -> Value<'gc> {
+    pub(crate) fn relax(self) -> Value<'gc> {
         self.0
     }
 }
@@ -468,13 +477,6 @@ impl<'gc> Deref for StrictValue<'gc> {
     }
 }
 
-impl Clone for StrictValue<'_> {
-    #[inline]
-    fn clone(&self) -> Self {
-        Self(self.0.clone())
-    }
-}
-
 impl fmt::Debug for StrictValue<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(&self.0, f)

fix/src/store.rs

@@ -7,7 +7,6 @@ mod validation;
 
 pub use config::StoreConfig;
 pub use daemon::DaemonStore;
-pub use validation::validate_store_path;
 
 pub trait Store: Send + Sync {
     fn get_store_dir(&self) -> &str;

fix/src/store/daemon.rs

@@ -69,13 +69,10 @@ impl Store for DaemonStore {
     fn ensure_path(&self, path: &str) -> Result<()> {
         self.block_on(async {
             self.connection.ensure_path(path).await.map_err(|e| {
-                Error::eval_error(
-                    format!(
+                Error::eval_error(format!(
                     "builtins.storePath: path '{}' is not valid in nix store: {}",
                     path, e
-                    ),
-                    None,
-                )
+                ))
             })
         })
     }

fix/src/store/validation.rs

@@ -2,75 +2,72 @@ use crate::error::{Error, Result};
 
 pub fn validate_store_path(store_dir: &str, path: &str) -> Result<()> {
     if !path.starts_with(store_dir) {
-        return Err(Error::eval_error(
-            format!("path '{}' is not in the Nix store", path),
-            None,
-        ));
+        return Err(Error::eval_error(format!(
+            "path '{}' is not in the Nix store",
+            path
+        )));
     }
 
     let relative = path
         .strip_prefix(store_dir)
         .and_then(|s| s.strip_prefix('/'))
-        .ok_or_else(|| Error::eval_error(format!("invalid store path format: {}", path), None))?;
+        .ok_or_else(|| Error::eval_error(format!("invalid store path format: {}", path)))?;
 
     if relative.is_empty() {
-        return Err(Error::eval_error(
-            format!("store path cannot be store directory itself: {}", path),
-            None,
-        ));
+        return Err(Error::eval_error(format!(
+            "store path cannot be store directory itself: {}",
+            path
+        )));
     }
 
     let parts: Vec<&str> = relative.splitn(2, '-').collect();
     if parts.len() != 2 {
-        return Err(Error::eval_error(
-            format!("invalid store path format (missing name): {}", path),
-            None,
-        ));
+        return Err(Error::eval_error(format!(
+            "invalid store path format (missing name): {}",
+            path
+        )));
     }
 
     let hash = parts[0];
     let name = parts[1];
 
     if hash.len() != 32 {
-        return Err(Error::eval_error(
-            format!(
+        return Err(Error::eval_error(format!(
             "invalid store path hash length (expected 32, got {}): {}",
             hash.len(),
             hash
-            ),
-            None,
-        ));
+        )));
     }
 
     for ch in hash.chars() {
         if !matches!(ch, '0'..='9' | 'a'..='d' | 'f'..='n' | 'p'..='s' | 'v'..='z') {
-            return Err(Error::eval_error(
-                format!("invalid character '{}' in store path hash: {}", ch, hash),
-                None,
-            ));
+            return Err(Error::eval_error(format!(
+                "invalid character '{}' in store path hash: {}",
+                ch, hash
+            )));
         }
     }
 
     if name.is_empty() {
-        return Err(Error::eval_error(
-            format!("store path has empty name: {}", path),
-            None,
-        ));
+        return Err(Error::eval_error(format!(
+            "store path has empty name: {}",
+            path
+        )));
     }
 
     if name.starts_with('.') {
-        return Err(Error::eval_error(
-            format!("store path name cannot start with '.': {}", name),
-            None,
-        ));
+        return Err(Error::eval_error(format!(
+            "store path name cannot start with '.': {}",
+            name
+        )));
     }
 
     for ch in name.chars() {
         if !matches!(ch, '0'..='9' | 'a'..='z' | 'A'..='Z' | '+' | '-' | '.' | '_' | '?' | '=') {
-            return Err(Error::eval_error(
-                format!("invalid character '{}' in store path name: {}", ch, name),
-                None,
-            ));
+            return Err(Error::eval_error(format!(
+                "invalid character '{}' in store path name: {}",
+                ch, name
+            )));
         }
     }
 

fix/src/value.rs

@@ -267,6 +267,15 @@ fn escape_quote_string(s: &str) -> String {
     ret
 }
 
+/// Wrapper to format a float in Nix style (C printf `%g` with precision 6).
+pub(crate) struct NixFloat(pub f64);
+
+impl Display for NixFloat {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        fmt_nix_float(f, self.0)
+    }
+}
+
 /// Format a float matching C's `printf("%g", x)` with default precision 6.
 fn fmt_nix_float(f: &mut Formatter<'_>, x: f64) -> FmtResult {
     if !x.is_finite() {

fix/tests/tests/basic_eval.rs

@@ -1,69 +0,0 @@
-use fix::value::Value;
-
-use crate::utils::{eval, eval_result};
-
-#[test_log::test]
-fn arithmetic() {
-    assert_eq!(eval("1 + 1"), Value::Int(2));
-}
-
-#[test_log::test]
-fn simple_function_application() {
-    assert_eq!(eval("(x: x) 1"), Value::Int(1));
-}
-
-#[test_log::test]
-fn curried_function() {
-    assert_eq!(eval("(x: y: x - y) 2 1"), Value::Int(1));
-}
-
-#[test_log::test]
-fn rec_attrset() {
-    assert_eq!(eval("rec { b = a; a = 1; }.b"), Value::Int(1));
-}
-
-#[test_log::test]
-fn let_binding() {
-    assert_eq!(eval("let b = a; a = 1; in b"), Value::Int(1));
-}
-
-#[test_log::test]
-fn fibonacci() {
-    assert_eq!(
-        eval(
-            "let fib = n: if n == 1 || n == 2 then 1 else (fib (n - 1)) + (fib (n - 2)); in fib 30"
-        ),
-        Value::Int(832040)
-    );
-}
-
-#[test_log::test]
-fn fixed_point_combinator() {
-    assert_eq!(
-        eval("((f: let x = f x; in x)(self: { x = 1; y = self.x + 1; })).y"),
-        Value::Int(2)
-    );
-}
-
-#[test_log::test]
-fn conditional_true() {
-    assert_eq!(eval("if true then 1 else 0"), Value::Int(1));
-}
-
-#[test_log::test]
-fn conditional_false() {
-    assert_eq!(eval("if false then 1 else 0"), Value::Int(0));
-}
-
-#[test_log::test]
-fn nested_let() {
-    assert_eq!(
-        eval("let x = 1; in let y = x + 1; z = y + 1; in z"),
-        Value::Int(3)
-    );
-}
-
-#[test_log::test]
-fn rec_inherit_fails() {
-    assert!(eval_result("{ inherit x; }").is_err());
-}

fix/tests/tests/builtins.rs

@@ -1,326 +0,0 @@
-use std::collections::BTreeMap;
-
-use fix::value::{AttrSet, List, Value};
-
-use crate::utils::eval;
-
-#[test_log::test]
-fn builtins_accessible() {
-    let result = eval("builtins");
-    assert!(matches!(result, Value::AttrSet(_)));
-}
-
-#[test_log::test]
-fn builtins_self_reference() {
-    let result = eval("builtins.builtins");
-    assert!(matches!(result, Value::AttrSet(_)));
-}
-
-#[test_log::test]
-fn builtins_add() {
-    assert_eq!(eval("builtins.add 1 2"), Value::Int(3));
-}
-
-#[test_log::test]
-fn builtins_length() {
-    assert_eq!(eval("builtins.length [1 2 3]"), Value::Int(3));
-}
-
-#[test_log::test]
-fn builtins_map() {
-    assert_eq!(
-        eval("builtins.map (x: x * 2) [1 2 3]"),
-        Value::List(List::new(vec![Value::Int(2), Value::Int(4), Value::Int(6)]))
-    );
-}
-
-#[test_log::test]
-fn builtins_filter() {
-    assert_eq!(
-        eval("builtins.filter (x: x > 1) [1 2 3]"),
-        Value::List(List::new(vec![Value::Int(2), Value::Int(3)]))
-    );
-}
-
-#[test_log::test]
-fn builtins_attrnames() {
-    let result = eval("builtins.attrNames { a = 1; b = 2; }");
-    assert!(matches!(result, Value::List(_)));
-    if let Value::List(list) = result {
-        assert_eq!(format!("{:?}", list).matches(',').count() + 1, 2);
-    }
-}
-
-#[test_log::test]
-fn builtins_head() {
-    assert_eq!(eval("builtins.head [1 2 3]"), Value::Int(1));
-}
-
-#[test_log::test]
-fn builtins_tail() {
-    assert_eq!(
-        eval("builtins.tail [1 2 3]"),
-        Value::List(List::new(vec![Value::Int(2), Value::Int(3)]))
-    );
-}
-
-#[test_log::test]
-fn builtins_in_let() {
-    assert_eq!(eval("let b = builtins; in b.add 5 3"), Value::Int(8));
-}
-
-#[test_log::test]
-fn builtins_in_with() {
-    assert_eq!(eval("with builtins; add 10 20"), Value::Int(30));
-}
-
-#[test_log::test]
-fn builtins_nested_calls() {
-    assert_eq!(
-        eval("builtins.add (builtins.mul 2 3) (builtins.sub 10 5)"),
-        Value::Int(11)
-    );
-}
-
-#[test_log::test]
-fn builtins_is_list() {
-    assert_eq!(eval("builtins.isList [1 2 3]"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn builtins_is_attrs() {
-    assert_eq!(eval("builtins.isAttrs { a = 1; }"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn builtins_is_function() {
-    assert_eq!(eval("builtins.isFunction (x: x)"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn builtins_is_null() {
-    assert_eq!(eval("builtins.isNull null"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn builtins_is_bool() {
-    assert_eq!(eval("builtins.isBool true"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn builtins_shadowing() {
-    assert_eq!(
-        eval("let builtins = { add = x: y: x - y; }; in builtins.add 5 3"),
-        Value::Int(2)
-    );
-}
-
-#[test_log::test]
-fn builtins_lazy_evaluation() {
-    let result = eval("builtins.builtins.builtins.add 1 1");
-    assert_eq!(result, Value::Int(2));
-}
-
-#[test_log::test]
-fn builtins_foldl() {
-    assert_eq!(
-        eval("builtins.foldl' (acc: x: acc + x) 0 [1 2 3 4 5]"),
-        Value::Int(15)
-    );
-}
-
-#[test_log::test]
-fn builtins_elem() {
-    assert_eq!(eval("builtins.elem 2 [1 2 3]"), Value::Bool(true));
-    assert_eq!(eval("builtins.elem 5 [1 2 3]"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn builtins_concat_lists() {
-    assert_eq!(
-        eval("builtins.concatLists [[1 2] [3 4] [5]]"),
-        Value::List(List::new(vec![
-            Value::Int(1),
-            Value::Int(2),
-            Value::Int(3),
-            Value::Int(4),
-            Value::Int(5)
-        ]))
-    );
-}
-
-#[test_log::test]
-fn builtins_compare_versions_basic() {
-    assert_eq!(
-        eval("builtins.compareVersions \"1.0\" \"2.3\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.1\" \"2.3\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3\" \"2.3\""),
-        Value::Int(0)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.5\" \"2.3\""),
-        Value::Int(1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"3.1\" \"2.3\""),
-        Value::Int(1)
-    );
-}
-
-#[test_log::test]
-fn builtins_compare_versions_components() {
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3.1\" \"2.3\""),
-        Value::Int(1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3\" \"2.3.1\""),
-        Value::Int(-1)
-    );
-}
-
-#[test_log::test]
-fn builtins_compare_versions_numeric_vs_alpha() {
-    // Numeric component comes before alpha component
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3.1\" \"2.3a\""),
-        Value::Int(1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3a\" \"2.3.1\""),
-        Value::Int(-1)
-    );
-}
-
-#[test_log::test]
-fn builtins_compare_versions_pre() {
-    // "pre" is special: comes before everything except another "pre"
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3pre1\" \"2.3\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3pre3\" \"2.3pre12\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3pre1\" \"2.3c\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3pre1\" \"2.3q\""),
-        Value::Int(-1)
-    );
-}
-
-#[test_log::test]
-fn builtins_compare_versions_alpha() {
-    // Alphabetic comparison
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3a\" \"2.3c\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3c\" \"2.3a\""),
-        Value::Int(1)
-    );
-}
-
-#[test_log::test]
-fn builtins_compare_versions_symmetry() {
-    // Test symmetry: compareVersions(a, b) == -compareVersions(b, a)
-    assert_eq!(
-        eval("builtins.compareVersions \"1.0\" \"2.3\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"2.3\" \"1.0\""),
-        Value::Int(1)
-    );
-}
-
-#[test_log::test]
-fn builtins_compare_versions_complex() {
-    // Complex version strings with multiple components
-    assert_eq!(
-        eval("builtins.compareVersions \"1.2.3.4\" \"1.2.3.5\""),
-        Value::Int(-1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"1.2.10\" \"1.2.9\""),
-        Value::Int(1)
-    );
-    assert_eq!(
-        eval("builtins.compareVersions \"1.2a3\" \"1.2a10\""),
-        Value::Int(-1)
-    );
-}
-
-#[test_log::test]
-fn builtins_generic_closure() {
-    assert_eq!(
-        eval(
-            "with builtins; length (genericClosure { startSet = [ { key = 1; } ]; operator = { key }: [ { key = key / 1.; } ]; a = 1; })"
-        ),
-        Value::Int(1),
-    );
-    assert_eq!(
-        eval(
-            "with builtins; (elemAt (genericClosure { startSet = [ { key = 1; } ]; operator = { key }: [ { key = key / 1.; } ]; a = 1; }) 0).key"
-        ),
-        Value::Int(1),
-    );
-}
-
-#[test_log::test]
-fn builtins_function_args() {
-    assert_eq!(
-        eval("builtins.functionArgs (x: 1)"),
-        Value::AttrSet(AttrSet::default())
-    );
-    assert_eq!(
-        eval("builtins.functionArgs ({}: 1)"),
-        Value::AttrSet(AttrSet::default())
-    );
-    assert_eq!(
-        eval("builtins.functionArgs ({...}: 1)"),
-        Value::AttrSet(AttrSet::default())
-    );
-    assert_eq!(
-        eval("builtins.functionArgs ({a}: 1)"),
-        Value::AttrSet(AttrSet::new(BTreeMap::from([(
-            "a".into(),
-            Value::Bool(false)
-        )])))
-    );
-    assert_eq!(
-        eval("builtins.functionArgs ({a, b ? 1}: 1)"),
-        Value::AttrSet(AttrSet::new(BTreeMap::from([
-            ("a".into(), Value::Bool(false)),
-            ("b".into(), Value::Bool(true))
-        ])))
-    );
-    assert_eq!(
-        eval("builtins.functionArgs ({a, b ? 1, ...}: 1)"),
-        Value::AttrSet(AttrSet::new(BTreeMap::from([
-            ("a".into(), Value::Bool(false)),
-            ("b".into(), Value::Bool(true))
-        ])))
-    );
-}
-
-#[test_log::test]
-fn builtins_parse_drv_name() {
-    let result = eval(r#"builtins.parseDrvName "nix-js-0.1.0pre""#).unwrap_attr_set();
-    assert_eq!(result.get("name"), Some(&Value::String("nix-js".into())));
-    assert_eq!(
-        result.get("version"),
-        Some(&Value::String("0.1.0pre".into()))
-    );
-}

fix/tests/tests/builtins_store.rs

@@ -1,193 +0,0 @@
-use fix::value::Value;
-
-use crate::utils::eval_result;
-
-#[test_log::test]
-fn to_file_simple() {
-    let result =
-        eval_result(r#"builtins.toFile "hello.txt" "Hello, World!""#).expect("Failed to evaluate");
-
-    match result {
-        Value::String(path) => {
-            assert!(path.contains("-hello.txt"));
-            assert!(std::path::Path::new(&path).exists());
-
-            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
-            assert_eq!(contents, "Hello, World!");
-        }
-        _ => panic!("Expected string, got {:?}", result),
-    }
-}
-
-#[test_log::test]
-fn to_file_with_references() {
-    let result = eval_result(
-        r#"
-            let
-              dep = builtins.toFile "dep.txt" "dependency";
-            in
-              builtins.toFile "main.txt" "Reference: ${dep}"
-        "#,
-    )
-    .expect("Failed to evaluate");
-
-    match result {
-        Value::String(path) => {
-            assert!(path.contains("-main.txt"));
-            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
-            assert!(contents.contains("Reference: "));
-            assert!(contents.contains("-dep.txt"));
-        }
-        _ => panic!("Expected string"),
-    }
-}
-
-#[test_log::test]
-fn to_file_invalid_name_with_slash() {
-    let result = eval_result(r#"builtins.toFile "foo/bar.txt" "content""#);
-
-    assert!(result.is_err());
-    assert!(
-        result
-            .unwrap_err()
-            .to_string()
-            .contains("name cannot contain '/'")
-    );
-}
-
-#[test_log::test]
-fn to_file_invalid_name_dot() {
-    let result = eval_result(r#"builtins.toFile "." "content""#);
-
-    assert!(result.is_err());
-    assert!(result.unwrap_err().to_string().contains("invalid name"));
-}
-
-#[test_log::test]
-fn to_file_invalid_name_dotdot() {
-    let result = eval_result(r#"builtins.toFile ".." "content""#);
-
-    assert!(result.is_err());
-    assert!(result.unwrap_err().to_string().contains("invalid name"));
-}
-
-#[test_log::test]
-fn store_path_validation_not_in_store() {
-    let result = eval_result(r#"builtins.storePath "/tmp/foo""#);
-
-    assert!(result.is_err());
-    assert!(
-        result
-            .unwrap_err()
-            .to_string()
-            .contains("not in the Nix store")
-    );
-}
-
-#[test_log::test]
-fn store_path_validation_malformed_hash() {
-    let dummy_file_result = eval_result(r#"builtins.toFile "dummy.txt" "content""#)
-        .expect("Failed to create dummy file");
-
-    let dummy_path = match dummy_file_result {
-        Value::String(ref p) => p.clone(),
-        _ => panic!("Expected string"),
-    };
-
-    let store_dir = std::path::Path::new(&dummy_path)
-        .parent()
-        .expect("Failed to get parent dir")
-        .to_str()
-        .expect("Failed to convert to string");
-
-    let test_path = format!("{}/invalid-hash-hello", store_dir);
-    let result = eval_result(&format!(r#"builtins.storePath "{}""#, test_path));
-
-    assert!(result.is_err());
-    let err_str = result.unwrap_err().to_string();
-    assert!(
-        err_str.contains("invalid") || err_str.contains("hash"),
-        "Expected hash validation error, got: {}",
-        err_str
-    );
-}
-
-#[test_log::test]
-fn store_path_validation_missing_name() {
-    let dummy_file_result = eval_result(r#"builtins.toFile "dummy.txt" "content""#)
-        .expect("Failed to create dummy file");
-
-    let dummy_path = match dummy_file_result {
-        Value::String(ref p) => p.clone(),
-        _ => panic!("Expected string"),
-    };
-
-    let store_dir = std::path::Path::new(&dummy_path)
-        .parent()
-        .expect("Failed to get parent dir")
-        .to_str()
-        .expect("Failed to convert to string");
-
-    let test_path = format!("{}/abcd1234abcd1234abcd1234abcd1234", store_dir);
-    let result = eval_result(&format!(r#"builtins.storePath "{}""#, test_path));
-
-    assert!(result.is_err());
-    let err_str = result.unwrap_err().to_string();
-    assert!(
-        err_str.contains("missing name") || err_str.contains("format"),
-        "Expected missing name error, got: {}",
-        err_str
-    );
-}
-
-#[test_log::test]
-fn to_file_curried_application() {
-    let result = eval_result(
-        r#"
-            let
-              makeFile = builtins.toFile "test.txt";
-            in
-              makeFile "test content"
-        "#,
-    )
-    .expect("Failed to evaluate");
-
-    match result {
-        Value::String(path) => {
-            assert!(path.contains("-test.txt"));
-            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
-            assert_eq!(contents, "test content");
-        }
-        _ => panic!("Expected string"),
-    }
-}
-
-#[test_log::test]
-fn to_file_number_conversion() {
-    let result = eval_result(r#"builtins.toFile "number.txt" (builtins.toString 42)"#)
-        .expect("Failed to evaluate");
-
-    match result {
-        Value::String(path) => {
-            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
-            assert_eq!(contents, "42");
-        }
-        _ => panic!("Expected string"),
-    }
-}
-
-#[test_log::test]
-fn to_file_list_conversion() {
-    let result = eval_result(
-        r#"builtins.toFile "list.txt" (builtins.concatStringsSep "\n" ["line1" "line2" "line3"])"#,
-    )
-    .expect("Failed to evaluate");
-
-    match result {
-        Value::String(path) => {
-            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
-            assert_eq!(contents, "line1\nline2\nline3");
-        }
-        _ => panic!("Expected string"),
-    }
-}

fix/tests/tests/free_globals.rs

@@ -1,74 +0,0 @@
-use fix::value::{List, Value};
-
-use crate::utils::{eval, eval_result};
-
-#[test_log::test]
-fn true_literal() {
-    assert_eq!(eval("true"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn false_literal() {
-    assert_eq!(eval("false"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn null_literal() {
-    assert_eq!(eval("null"), Value::Null);
-}
-
-#[test_log::test]
-fn map_function() {
-    assert_eq!(
-        eval("map (x: x * 2) [1 2 3]"),
-        Value::List(List::new(vec![Value::Int(2), Value::Int(4), Value::Int(6)]))
-    );
-}
-
-#[test_log::test]
-fn is_null_function() {
-    assert_eq!(eval("isNull null"), Value::Bool(true));
-    assert_eq!(eval("isNull 5"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn shadow_true() {
-    assert_eq!(eval("let true = false; in true"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn shadow_map() {
-    assert_eq!(eval("let map = x: y: x; in map 1 2"), Value::Int(1));
-}
-
-#[test_log::test]
-fn mixed_usage() {
-    assert_eq!(
-        eval("if true then map (x: x + 1) [1 2] else []"),
-        Value::List(List::new(vec![Value::Int(2), Value::Int(3)]))
-    );
-}
-
-#[test_log::test]
-fn in_let_bindings() {
-    assert_eq!(
-        eval("let x = true; y = false; in x && y"),
-        Value::Bool(false)
-    );
-}
-
-#[test_log::test]
-fn shadow_in_function() {
-    assert_eq!(eval("(true: true) false"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn throw_function() {
-    let result = eval_result("throw \"error message\"");
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn to_string_function() {
-    assert_eq!(eval("toString 42"), Value::String("42".to_string()));
-}

fix/tests/tests/functions.rs

@@ -1,120 +0,0 @@
-use fix::value::Value;
-
-use crate::utils::{eval, eval_result};
-
-#[test_log::test]
-fn required_parameters() {
-    assert_eq!(eval("({ a, b }: a + b) { a = 1; b = 2; }"), Value::Int(3));
-}
-
-#[test_log::test]
-fn missing_required_parameter() {
-    let result = eval_result("({ a, b }: a + b) { a = 1; }");
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn all_required_parameters_present() {
-    assert_eq!(
-        eval("({ x, y, z }: x + y + z) { x = 1; y = 2; z = 3; }"),
-        Value::Int(6)
-    );
-}
-
-#[test_log::test]
-fn reject_unexpected_arguments() {
-    let result = eval_result("({ a, b }: a + b) { a = 1; b = 2; c = 3; }");
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn ellipsis_accepts_extra_arguments() {
-    assert_eq!(
-        eval("({ a, b, ... }: a + b) { a = 1; b = 2; c = 3; }"),
-        Value::Int(3)
-    );
-}
-
-#[test_log::test]
-fn default_parameters() {
-    assert_eq!(eval("({ a, b ? 5 }: a + b) { a = 1; }"), Value::Int(6));
-}
-
-#[test_log::test]
-fn override_default_parameter() {
-    assert_eq!(
-        eval("({ a, b ? 5 }: a + b) { a = 1; b = 10; }"),
-        Value::Int(11)
-    );
-}
-
-#[test_log::test]
-fn at_pattern_alias() {
-    assert_eq!(
-        eval("(args@{ a, b }: args.a + args.b) { a = 1; b = 2; }"),
-        Value::Int(3)
-    );
-}
-
-#[test_log::test]
-fn simple_parameter_no_validation() {
-    assert_eq!(eval("(x: x.a + x.b) { a = 1; b = 2; }"), Value::Int(3));
-}
-
-#[test_log::test]
-fn simple_parameter_accepts_any_argument() {
-    assert_eq!(eval("(x: x) 42"), Value::Int(42));
-}
-
-#[test_log::test]
-fn nested_function_parameters() {
-    assert_eq!(
-        eval("({ a }: { b }: a + b) { a = 5; } { b = 3; }"),
-        Value::Int(8)
-    );
-}
-
-#[test_log::test]
-fn pattern_param_simple_reference_in_default() {
-    assert_eq!(eval("({ a, b ? a }: b) { a = 10; }"), Value::Int(10));
-}
-
-#[test_log::test]
-fn pattern_param_multiple_references_in_default() {
-    assert_eq!(
-        eval("({ a, b ? a + 5, c ? 1 }: b + c) { a = 10; }"),
-        Value::Int(16)
-    );
-}
-
-#[test_log::test]
-fn pattern_param_mutual_reference() {
-    assert_eq!(
-        eval("({ a, b ? c + 1, c ? 5 }: b) { a = 1; }"),
-        Value::Int(6)
-    );
-}
-
-#[test_log::test]
-fn pattern_param_override_mutual_reference() {
-    assert_eq!(
-        eval("({ a, b ? c + 1, c ? 5 }: b) { a = 1; c = 10; }"),
-        Value::Int(11)
-    );
-}
-
-#[test_log::test]
-fn pattern_param_reference_list() {
-    assert_eq!(
-        eval("({ a, b ? [ a 2 ] }: builtins.elemAt b 0) { a = 42; }"),
-        Value::Int(42)
-    );
-}
-
-#[test_log::test]
-fn pattern_param_alias_in_default() {
-    assert_eq!(
-        eval("(args@{ a, b ? args.a + 10 }: b) { a = 5; }"),
-        Value::Int(15)
-    );
-}

fix/tests/tests/io_operations.rs

@@ -366,3 +366,193 @@ fn read_dir_on_file_fails() {
     let err_msg = result.unwrap_err().to_string();
     assert!(err_msg.contains("not a directory"));
 }
+
+#[test_log::test]
+fn to_file_simple() {
+    let result =
+        eval_result(r#"builtins.toFile "hello.txt" "Hello, World!""#).expect("Failed to evaluate");
+
+    match result {
+        Value::String(path) => {
+            assert!(path.contains("-hello.txt"));
+            assert!(std::path::Path::new(&path).exists());
+
+            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
+            assert_eq!(contents, "Hello, World!");
+        }
+        _ => panic!("Expected string, got {:?}", result),
+    }
+}
+
+#[test_log::test]
+fn to_file_with_references() {
+    let result = eval_result(
+        r#"
+            let
+              dep = builtins.toFile "dep.txt" "dependency";
+            in
+              builtins.toFile "main.txt" "Reference: ${dep}"
+        "#,
+    )
+    .expect("Failed to evaluate");
+
+    match result {
+        Value::String(path) => {
+            assert!(path.contains("-main.txt"));
+            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
+            assert!(contents.contains("Reference: "));
+            assert!(contents.contains("-dep.txt"));
+        }
+        _ => panic!("Expected string"),
+    }
+}
+
+#[test_log::test]
+fn to_file_invalid_name_with_slash() {
+    let result = eval_result(r#"builtins.toFile "foo/bar.txt" "content""#);
+
+    assert!(result.is_err());
+    assert!(
+        result
+            .unwrap_err()
+            .to_string()
+            .contains("name cannot contain '/'")
+    );
+}
+
+#[test_log::test]
+fn to_file_invalid_name_dot() {
+    let result = eval_result(r#"builtins.toFile "." "content""#);
+
+    assert!(result.is_err());
+    assert!(result.unwrap_err().to_string().contains("invalid name"));
+}
+
+#[test_log::test]
+fn to_file_invalid_name_dotdot() {
+    let result = eval_result(r#"builtins.toFile ".." "content""#);
+
+    assert!(result.is_err());
+    assert!(result.unwrap_err().to_string().contains("invalid name"));
+}
+
+#[test_log::test]
+fn store_path_validation_not_in_store() {
+    let result = eval_result(r#"builtins.storePath "/tmp/foo""#);
+
+    assert!(result.is_err());
+    assert!(
+        result
+            .unwrap_err()
+            .to_string()
+            .contains("not in the Nix store")
+    );
+}
+
+#[test_log::test]
+fn store_path_validation_malformed_hash() {
+    let dummy_file_result = eval_result(r#"builtins.toFile "dummy.txt" "content""#)
+        .expect("Failed to create dummy file");
+
+    let dummy_path = match dummy_file_result {
+        Value::String(ref p) => p.clone(),
+        _ => panic!("Expected string"),
+    };
+
+    let store_dir = std::path::Path::new(&dummy_path)
+        .parent()
+        .expect("Failed to get parent dir")
+        .to_str()
+        .expect("Failed to convert to string");
+
+    let test_path = format!("{}/invalid-hash-hello", store_dir);
+    let result = eval_result(&format!(r#"builtins.storePath "{}""#, test_path));
+
+    assert!(result.is_err());
+    let err_str = result.unwrap_err().to_string();
+    assert!(
+        err_str.contains("invalid") || err_str.contains("hash"),
+        "Expected hash validation error, got: {}",
+        err_str
+    );
+}
+
+#[test_log::test]
+fn store_path_validation_missing_name() {
+    let dummy_file_result = eval_result(r#"builtins.toFile "dummy.txt" "content""#)
+        .expect("Failed to create dummy file");
+
+    let dummy_path = match dummy_file_result {
+        Value::String(ref p) => p.clone(),
+        _ => panic!("Expected string"),
+    };
+
+    let store_dir = std::path::Path::new(&dummy_path)
+        .parent()
+        .expect("Failed to get parent dir")
+        .to_str()
+        .expect("Failed to convert to string");
+
+    let test_path = format!("{}/abcd1234abcd1234abcd1234abcd1234", store_dir);
+    let result = eval_result(&format!(r#"builtins.storePath "{}""#, test_path));
+
+    assert!(result.is_err());
+    let err_str = result.unwrap_err().to_string();
+    assert!(
+        err_str.contains("missing name") || err_str.contains("format"),
+        "Expected missing name error, got: {}",
+        err_str
+    );
+}
+
+#[test_log::test]
+fn to_file_curried_application() {
+    let result = eval_result(
+        r#"
+            let
+              makeFile = builtins.toFile "test.txt";
+            in
+              makeFile "test content"
+        "#,
+    )
+    .expect("Failed to evaluate");
+
+    match result {
+        Value::String(path) => {
+            assert!(path.contains("-test.txt"));
+            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
+            assert_eq!(contents, "test content");
+        }
+        _ => panic!("Expected string"),
+    }
+}
+
+#[test_log::test]
+fn to_file_number_conversion() {
+    let result = eval_result(r#"builtins.toFile "number.txt" (builtins.toString 42)"#)
+        .expect("Failed to evaluate");
+
+    match result {
+        Value::String(path) => {
+            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
+            assert_eq!(contents, "42");
+        }
+        _ => panic!("Expected string"),
+    }
+}
+
+#[test_log::test]
+fn to_file_list_conversion() {
+    let result = eval_result(
+        r#"builtins.toFile "list.txt" (builtins.concatStringsSep "\n" ["line1" "line2" "line3"])"#,
+    )
+    .expect("Failed to evaluate");
+
+    match result {
+        Value::String(path) => {
+            let contents = std::fs::read_to_string(&path).expect("Failed to read file");
+            assert_eq!(contents, "line1\nline2\nline3");
+        }
+        _ => panic!("Expected string"),
+    }
+}

fix/tests/tests/main.rs

@@ -1,17 +1,6 @@
-mod basic_eval;
-mod builtins;
-mod builtins_store;
 mod derivation;
 mod findfile;
-mod free_globals;
-mod functions;
 mod io_operations;
 mod lang;
-mod numeric_types;
-mod operators;
-mod path_operations;
-mod regex;
 mod string_context;
-mod thunk_scope;
-mod to_string;
 mod utils;

fix/tests/tests/numeric_types.rs

@@ -1,138 +0,0 @@
-use fix::value::Value;
-
-use crate::utils::eval;
-
-#[test_log::test]
-fn large_i64_max() {
-    assert_eq!(eval("9223372036854775807"), Value::Int(9223372036854775807));
-}
-
-#[test_log::test]
-fn large_i64_negative() {
-    assert_eq!(
-        eval("-9223372036854775807"),
-        Value::Int(-9223372036854775807)
-    );
-}
-
-#[test_log::test]
-fn large_number_arithmetic() {
-    assert_eq!(
-        eval("5000000000000000000 + 3000000000000000000"),
-        Value::Int(8000000000000000000i64)
-    );
-}
-
-#[test_log::test]
-fn is_int_with_int() {
-    assert_eq!(eval("builtins.isInt 42"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn is_int_with_float() {
-    assert_eq!(eval("builtins.isInt 42.0"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn is_float_with_int() {
-    assert_eq!(eval("builtins.isFloat 42"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn is_float_with_float() {
-    assert_eq!(eval("builtins.isFloat 42.5"), Value::Bool(true));
-    assert_eq!(eval("builtins.isFloat 1.0"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn typeof_int() {
-    assert_eq!(eval("builtins.typeOf 1"), Value::String("int".to_string()));
-}
-
-#[test_log::test]
-fn typeof_float() {
-    assert_eq!(
-        eval("builtins.typeOf 1.0"),
-        Value::String("float".to_string())
-    );
-    assert_eq!(
-        eval("builtins.typeOf 3.14"),
-        Value::String("float".to_string())
-    );
-}
-
-#[test_log::test]
-fn int_literal() {
-    assert_eq!(eval("1"), Value::Int(1));
-}
-
-#[test_log::test]
-fn float_literal() {
-    assert_eq!(eval("1."), Value::Float(1.));
-}
-
-#[test_log::test]
-fn int_plus_int() {
-    assert_eq!(
-        eval("builtins.typeOf (1 + 2)"),
-        Value::String("int".to_string())
-    );
-}
-
-#[test_log::test]
-fn int_plus_float() {
-    assert_eq!(
-        eval("builtins.typeOf (1 + 2.0)"),
-        Value::String("float".to_string())
-    );
-}
-
-#[test_log::test]
-fn int_times_int() {
-    assert_eq!(
-        eval("builtins.typeOf (3 * 4)"),
-        Value::String("int".to_string())
-    );
-}
-
-#[test_log::test]
-fn int_times_float() {
-    assert_eq!(
-        eval("builtins.typeOf (3 * 4.0)"),
-        Value::String("float".to_string())
-    );
-}
-
-#[test_log::test]
-fn integer_division() {
-    assert_eq!(eval("5 / 2"), Value::Int(2));
-    assert_eq!(eval("7 / 3"), Value::Int(2));
-    assert_eq!(eval("10 / 3"), Value::Int(3));
-}
-
-#[test_log::test]
-fn float_division() {
-    assert_eq!(eval("5 / 2.0"), Value::Float(2.5));
-    assert_eq!(eval("7.0 / 2"), Value::Float(3.5));
-}
-
-#[test_log::test]
-fn negative_integer_division() {
-    assert_eq!(eval("(-7) / 3"), Value::Int(-2));
-}
-
-#[test_log::test]
-fn builtin_add_with_large_numbers() {
-    assert_eq!(
-        eval("builtins.add 5000000000000000000 3000000000000000000"),
-        Value::Int(8000000000000000000i64)
-    );
-}
-
-#[test_log::test]
-fn builtin_mul_with_large_numbers() {
-    assert_eq!(
-        eval("builtins.mul 1000000000 1000000000"),
-        Value::Int(1000000000000000000i64)
-    );
-}

fix/tests/tests/operators.rs

@@ -1,144 +0,0 @@
-use std::collections::BTreeMap;
-
-use fix::value::{AttrSet, List, Symbol, Value};
-
-use crate::utils::eval;
-
-#[test_log::test]
-fn addition() {
-    assert_eq!(eval("1 + 1"), Value::Int(2));
-}
-
-#[test_log::test]
-fn subtraction() {
-    assert_eq!(eval("2 - 1"), Value::Int(1));
-}
-
-#[test_log::test]
-fn multiplication() {
-    assert_eq!(eval("1. * 1"), Value::Float(1.));
-}
-
-#[test_log::test]
-fn division() {
-    assert_eq!(eval("1 / 1."), Value::Float(1.));
-}
-
-#[test_log::test]
-fn equality() {
-    assert_eq!(eval("1 == 1"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn inequality() {
-    assert_eq!(eval("1 != 1"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn less_than() {
-    assert_eq!(eval("2 < 1"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn greater_than() {
-    assert_eq!(eval("2 > 1"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn less_than_or_equal() {
-    assert_eq!(eval("1 <= 1"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn greater_than_or_equal() {
-    assert_eq!(eval("1 >= 1"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn logical_or_short_circuit() {
-    assert_eq!(eval("true || (1 / 0)"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn logical_and() {
-    assert_eq!(eval("true && 1 == 0"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn list_concatenation() {
-    assert_eq!(
-        eval("[ 1 2 3 ] ++ [ 4 5 6 ]"),
-        Value::List(List::new((1..=6).map(Value::Int).collect()))
-    );
-}
-
-#[test_log::test]
-fn attrset_update() {
-    assert_eq!(
-        eval("{ a.b = 1; b = 2; } // { a.c = 2; }"),
-        Value::AttrSet(AttrSet::new(BTreeMap::from([
-            (
-                Symbol::from("a"),
-                Value::AttrSet(AttrSet::new(BTreeMap::from([(
-                    Symbol::from("c"),
-                    Value::Int(2),
-                )]))),
-            ),
-            (Symbol::from("b"), Value::Int(2)),
-        ])))
-    );
-}
-
-#[test_log::test]
-fn unary_negation() {
-    assert_eq!(eval("-5"), Value::Int(-5));
-}
-
-#[test_log::test]
-fn logical_not() {
-    assert_eq!(eval("!true"), Value::Bool(false));
-    assert_eq!(eval("!false"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn select_with_default_lazy_evaluation() {
-    assert_eq!(eval("{ a = 1; }.a or (1 / 0)"), Value::Int(1));
-}
-
-#[test_log::test]
-fn select_with_default_nested_lazy() {
-    assert_eq!(
-        eval("{ a.b = 42; }.a.b or (builtins.abort \"should not evaluate\")"),
-        Value::Int(42)
-    );
-}
-
-#[test_log::test]
-fn select_with_default_fallback() {
-    assert_eq!(eval("{ a = 1; }.b or 999"), Value::Int(999));
-}
-
-#[test_log::test]
-fn implication_false_false() {
-    assert_eq!(eval("false -> false"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn implication_false_true() {
-    assert_eq!(eval("false -> true"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn implication_true_false() {
-    assert_eq!(eval("true -> false"), Value::Bool(false));
-}
-
-#[test_log::test]
-fn implication_true_true() {
-    assert_eq!(eval("true -> true"), Value::Bool(true));
-}
-
-#[test_log::test]
-fn implication_short_circuit() {
-    assert_eq!(eval("false -> (1 / 0)"), Value::Bool(true));
-}

fix/tests/tests/path_operations.rs

@@ -1,117 +0,0 @@
-use fix::value::Value;
-
-use crate::utils::{eval, eval_result};
-
-#[test_log::test]
-fn path_type_of() {
-    let result = eval("builtins.typeOf ./foo");
-    assert_eq!(result, Value::String("path".to_string()));
-}
-
-#[test_log::test]
-fn is_path_true() {
-    let result = eval("builtins.isPath ./foo");
-    assert_eq!(result, Value::Bool(true));
-}
-
-#[test_log::test]
-fn is_path_false_string() {
-    let result = eval(r#"builtins.isPath "./foo""#);
-    assert_eq!(result, Value::Bool(false));
-}
-
-#[test_log::test]
-fn is_path_false_number() {
-    let result = eval("builtins.isPath 42");
-    assert_eq!(result, Value::Bool(false));
-}
-
-#[test_log::test]
-fn path_concat_type() {
-    // path + string = path
-    let result = eval(r#"builtins.typeOf (./foo + "/bar")"#);
-    assert_eq!(result, Value::String("path".to_string()));
-}
-
-#[test_log::test]
-fn string_path_concat_type() {
-    // string + path = string
-    let result = eval(r#"builtins.typeOf ("prefix-" + ./foo)"#);
-    assert_eq!(result, Value::String("string".to_string()));
-}
-
-#[test_log::test]
-fn basename_of_path() {
-    let result = eval("builtins.baseNameOf ./path/to/file.nix");
-    assert!(matches!(result, Value::String(s) if s == "file.nix"));
-}
-
-#[test_log::test]
-fn basename_of_string() {
-    let result = eval(r#"builtins.baseNameOf "/path/to/file.nix""#);
-    assert_eq!(result, Value::String("file.nix".to_string()));
-}
-
-#[test_log::test]
-fn dir_of_path_type() {
-    // dirOf preserves path type
-    let result = eval("builtins.typeOf (builtins.dirOf ./path/to/file.nix)");
-    assert_eq!(result, Value::String("path".to_string()));
-}
-
-#[test_log::test]
-fn dir_of_string_type() {
-    // dirOf preserves string type
-    let result = eval(r#"builtins.typeOf (builtins.dirOf "/path/to/file.nix")"#);
-    assert_eq!(result, Value::String("string".to_string()));
-}
-
-#[test_log::test]
-fn path_equality() {
-    // Same path should be equal
-    let result = eval("./foo == ./foo");
-    assert_eq!(result, Value::Bool(true));
-}
-
-#[test_log::test]
-fn path_not_equal_string() {
-    // Paths and strings are different types - should not be equal
-    let result = eval(r#"./foo == "./foo""#);
-    assert_eq!(result, Value::Bool(false));
-}
-
-#[test_log::test]
-fn to_path_absolute() {
-    // toPath with absolute path returns string
-    let result = eval(r#"builtins.toPath "/foo/bar""#);
-    assert_eq!(result, Value::String("/foo/bar".to_string()));
-}
-
-#[test_log::test]
-fn to_path_type_is_string() {
-    // toPath returns a string, not a path
-    let result = eval(r#"builtins.typeOf (builtins.toPath "/foo")"#);
-    assert_eq!(result, Value::String("string".to_string()));
-}
-
-#[test_log::test]
-fn to_path_relative_fails() {
-    // toPath with relative path should fail
-    let result = eval_result(r#"builtins.toPath "foo/bar""#);
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn to_path_empty_fails() {
-    // toPath with empty string should fail
-    let result = eval_result(r#"builtins.toPath """#);
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn to_path_from_path_value() {
-    // toPath can accept a path value too (coerces to string first)
-    let result = eval("builtins.toPath ./foo");
-    // Should succeed and return the absolute path as a string
-    assert!(matches!(result, Value::String(s) if s.starts_with("/")));
-}

fix/tests/tests/regex.rs

@@ -1,317 +0,0 @@
-use fix::value::{List, Value};
-
-use crate::utils::eval;
-use crate::utils::eval_result;
-
-#[test_log::test]
-fn match_exact_full_string() {
-    assert_eq!(
-        eval(r#"builtins.match "foobar" "foobar""#),
-        Value::List(List::new(vec![]))
-    );
-}
-
-#[test_log::test]
-fn match_partial_returns_null() {
-    assert_eq!(eval(r#"builtins.match "foo" "foobar""#), Value::Null);
-}
-
-#[test_log::test]
-fn match_with_capture_groups() {
-    assert_eq!(
-        eval(r#"builtins.match "(.*)\\.nix" "foobar.nix""#),
-        Value::List(List::new(vec![Value::String("foobar".into())]))
-    );
-}
-
-#[test_log::test]
-fn match_multiple_capture_groups() {
-    assert_eq!(
-        eval(r#"builtins.match "((.*)/)?([^/]*)\\.nix" "foobar.nix""#),
-        Value::List(List::new(vec![
-            Value::Null,
-            Value::Null,
-            Value::String("foobar".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn match_with_path() {
-    assert_eq!(
-        eval(r#"builtins.match "((.*)/)?([^/]*)\\.nix" "/path/to/foobar.nix""#),
-        Value::List(List::new(vec![
-            Value::String("/path/to/".into()),
-            Value::String("/path/to".into()),
-            Value::String("foobar".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn match_posix_space_class() {
-    assert_eq!(
-        eval(r#"builtins.match "[[:space:]]+([^[:space:]]+)[[:space:]]+" "  foo   ""#),
-        Value::List(List::new(vec![Value::String("foo".into())]))
-    );
-}
-
-#[test_log::test]
-fn match_posix_upper_class() {
-    assert_eq!(
-        eval(r#"builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" "  foo   ""#),
-        Value::Null
-    );
-
-    assert_eq!(
-        eval(r#"builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" "  FOO   ""#),
-        Value::List(List::new(vec![Value::String("FOO".into())]))
-    );
-}
-
-#[test_log::test]
-fn match_quantifiers() {
-    assert_eq!(
-        eval(r#"builtins.match "fo*" "f""#),
-        Value::List(List::new(vec![]))
-    );
-
-    assert_eq!(eval(r#"builtins.match "fo+" "f""#), Value::Null);
-
-    assert_eq!(
-        eval(r#"builtins.match "fo{1,2}" "foo""#),
-        Value::List(List::new(vec![]))
-    );
-
-    assert_eq!(eval(r#"builtins.match "fo{1,2}" "fooo""#), Value::Null);
-}
-
-#[test_log::test]
-fn split_non_capturing() {
-    assert_eq!(
-        eval(r#"builtins.split "foobar" "foobar""#),
-        Value::List(List::new(vec![
-            Value::String("".into()),
-            Value::List(List::new(vec![])),
-            Value::String("".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_no_match() {
-    assert_eq!(
-        eval(r#"builtins.split "fo+" "f""#),
-        Value::List(List::new(vec![Value::String("f".into())]))
-    );
-}
-
-#[test_log::test]
-fn split_with_capture_group() {
-    assert_eq!(
-        eval(r#"builtins.split "(fo*)" "foobar""#),
-        Value::List(List::new(vec![
-            Value::String("".into()),
-            Value::List(List::new(vec![Value::String("foo".into())])),
-            Value::String("bar".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_multiple_matches() {
-    assert_eq!(
-        eval(r#"builtins.split "(b)" "foobarbaz""#),
-        Value::List(List::new(vec![
-            Value::String("foo".into()),
-            Value::List(List::new(vec![Value::String("b".into())])),
-            Value::String("ar".into()),
-            Value::List(List::new(vec![Value::String("b".into())])),
-            Value::String("az".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_with_multiple_groups() {
-    assert_eq!(
-        eval(r#"builtins.split "(f)(o*)" "foo""#),
-        Value::List(List::new(vec![
-            Value::String("".into()),
-            Value::List(List::new(vec![
-                Value::String("f".into()),
-                Value::String("oo".into())
-            ])),
-            Value::String("".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_with_optional_groups() {
-    assert_eq!(
-        eval(r#"builtins.split "(a)|(c)" "abc""#),
-        Value::List(List::new(vec![
-            Value::String("".into()),
-            Value::List(List::new(vec![Value::String("a".into()), Value::Null])),
-            Value::String("b".into()),
-            Value::List(List::new(vec![Value::Null, Value::String("c".into())])),
-            Value::String("".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_greedy_matching() {
-    assert_eq!(
-        eval(r#"builtins.split "(o+)" "oooofoooo""#),
-        Value::List(List::new(vec![
-            Value::String("".into()),
-            Value::List(List::new(vec![Value::String("oooo".into())])),
-            Value::String("f".into()),
-            Value::List(List::new(vec![Value::String("oooo".into())])),
-            Value::String("".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_posix_classes() {
-    assert_eq!(
-        eval(r#"builtins.split "([[:upper:]]+)" "  FOO   ""#),
-        Value::List(List::new(vec![
-            Value::String("  ".into()),
-            Value::List(List::new(vec![Value::String("FOO".into())])),
-            Value::String("   ".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn replace_basic() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings ["o"] ["a"] "foobar""#),
-        Value::String("faabar".into())
-    );
-}
-
-#[test_log::test]
-fn replace_with_empty() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings ["o"] [""] "foobar""#),
-        Value::String("fbar".into())
-    );
-}
-
-#[test_log::test]
-fn replace_multiple_patterns() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings ["oo" "a"] ["a" "oo"] "foobar""#),
-        Value::String("faboor".into())
-    );
-}
-
-#[test_log::test]
-fn replace_first_match_wins() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings ["oo" "oo"] ["u" "i"] "foobar""#),
-        Value::String("fubar".into())
-    );
-}
-
-#[test_log::test]
-fn replace_empty_pattern() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings [""] ["X"] "abc""#),
-        Value::String("XaXbXcX".into())
-    );
-}
-
-#[test_log::test]
-fn replace_empty_pattern_empty_string() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings [""] ["X"] """#),
-        Value::String("X".into())
-    );
-}
-
-#[test_log::test]
-fn replace_simple_char() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings ["-"] ["_"] "a-b""#),
-        Value::String("a_b".into())
-    );
-}
-
-#[test_log::test]
-fn replace_longer_pattern() {
-    assert_eq!(
-        eval(r#"builtins.replaceStrings ["oo"] ["u"] "foobar""#),
-        Value::String("fubar".into())
-    );
-}
-
-#[test_log::test]
-fn replace_different_lengths() {
-    let result = eval_result(r#"builtins.replaceStrings ["a" "b"] ["x"] "test""#);
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn split_version_simple() {
-    assert_eq!(
-        eval(r#"builtins.splitVersion "1.2.3""#),
-        Value::List(List::new(vec![
-            Value::String("1".into()),
-            Value::String("2".into()),
-            Value::String("3".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_version_with_pre() {
-    assert_eq!(
-        eval(r#"builtins.splitVersion "2.3.0pre1234""#),
-        Value::List(List::new(vec![
-            Value::String("2".into()),
-            Value::String("3".into()),
-            Value::String("0".into()),
-            Value::String("pre".into()),
-            Value::String("1234".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_version_with_letters() {
-    assert_eq!(
-        eval(r#"builtins.splitVersion "2.3a""#),
-        Value::List(List::new(vec![
-            Value::String("2".into()),
-            Value::String("3".into()),
-            Value::String("a".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_version_with_dashes() {
-    assert_eq!(
-        eval(r#"builtins.splitVersion "2.3-beta1""#),
-        Value::List(List::new(vec![
-            Value::String("2".into()),
-            Value::String("3".into()),
-            Value::String("beta".into()),
-            Value::String("1".into())
-        ]))
-    );
-}
-
-#[test_log::test]
-fn split_version_empty() {
-    assert_eq!(
-        eval(r#"builtins.splitVersion """#),
-        Value::List(List::new(vec![]))
-    );
-}

fix/tests/tests/thunk_scope.rs

@@ -1,119 +0,0 @@
-use fix::value::Value;
-
-use crate::utils::eval;
-
-#[test_log::test]
-fn non_recursive_bindings() {
-    assert_eq!(eval("let x = 1; y = 2; z = x + y; in z"), Value::Int(3));
-}
-
-#[test_log::test]
-fn non_recursive_multiple_bindings() {
-    assert_eq!(
-        eval("let a = 10; b = 20; c = 30; d = a + b + c; in d"),
-        Value::Int(60)
-    );
-}
-
-#[test_log::test]
-fn recursive_fibonacci() {
-    assert_eq!(
-        eval("let fib = n: if n <= 1 then 1 else fib (n - 1) + fib (n - 2); in fib 5"),
-        Value::Int(8)
-    );
-}
-
-#[test_log::test]
-fn recursive_factorial() {
-    assert_eq!(
-        eval("let factorial = n: if n == 0 then 1 else n * factorial (n - 1); in factorial 5"),
-        Value::Int(120)
-    );
-}
-
-#[test_log::test]
-fn mutual_recursion_simple() {
-    assert_eq!(
-        eval(
-            "let f = n: if n == 0 then 0 else g (n - 1); g = n: if n == 0 then 1 else f (n - 1); in f 5"
-        ),
-        Value::Int(1)
-    );
-}
-
-#[test_log::test]
-fn mutual_recursion_even_odd() {
-    assert_eq!(
-        eval(
-            "let even = n: if n == 0 then true else odd (n - 1); odd = n: if n == 0 then false else even (n - 1); in even 4"
-        ),
-        Value::Bool(true)
-    );
-}
-
-#[test_log::test]
-fn mixed_recursive_and_non_recursive() {
-    assert_eq!(
-        eval("let x = 1; f = n: if n == 0 then x else f (n - 1); in f 5"),
-        Value::Int(1)
-    );
-}
-
-#[test_log::test]
-fn mixed_with_multiple_non_recursive() {
-    assert_eq!(
-        eval(
-            "let a = 10; b = 20; sum = a + b; countdown = n: if n == 0 then sum else countdown (n - 1); in countdown 3"
-        ),
-        Value::Int(30)
-    );
-}
-
-#[test_log::test]
-fn rec_attrset_non_recursive() {
-    assert_eq!(eval("rec { x = 1; y = 2; z = x + y; }.z"), Value::Int(3));
-}
-
-#[test_log::test]
-fn rec_attrset_recursive() {
-    assert_eq!(
-        eval("rec { f = n: if n == 0 then 0 else f (n - 1); }.f 10"),
-        Value::Int(0)
-    );
-}
-
-#[test_log::test]
-fn nested_let_non_recursive() {
-    assert_eq!(
-        eval("let x = 1; in let y = x + 1; z = y + 1; in z"),
-        Value::Int(3)
-    );
-}
-
-#[test_log::test]
-fn nested_let_with_recursive() {
-    assert_eq!(
-        eval("let f = n: if n == 0 then 0 else f (n - 1); in let g = m: f m; in g 5"),
-        Value::Int(0)
-    );
-}
-
-#[test_log::test]
-fn three_way_mutual_recursion() {
-    assert_eq!(
-        eval(
-            "let a = n: if n == 0 then 1 else b (n - 1); b = n: if n == 0 then 2 else c (n - 1); c = n: if n == 0 then 3 else a (n - 1); in a 6"
-        ),
-        Value::Int(1)
-    );
-}
-
-#[test_log::test]
-fn complex_mixed_dependencies() {
-    assert_eq!(
-        eval(
-            "let x = 5; y = 10; sum = x + y; fib = n: if n <= 1 then 1 else fib (n - 1) + fib (n - 2); result = sum + fib 5; in result"
-        ),
-        Value::Int(23)
-    );
-}

fix/tests/tests/to_string.rs

@@ -1,256 +0,0 @@
-use fix::value::Value;
-
-use crate::utils::{eval, eval_result};
-
-#[test_log::test]
-fn string_returns_as_is() {
-    assert_eq!(
-        eval(r#"toString "hello""#),
-        Value::String("hello".to_string())
-    );
-}
-
-#[test_log::test]
-fn integer_to_string() {
-    assert_eq!(eval("toString 42"), Value::String("42".to_string()));
-    assert_eq!(eval("toString (-5)"), Value::String("-5".to_string()));
-    assert_eq!(eval("toString 0"), Value::String("0".to_string()));
-}
-
-#[test_log::test]
-fn float_to_string() {
-    assert_eq!(eval("toString 3.14"), Value::String("3.14".to_string()));
-    assert_eq!(eval("toString 0.0"), Value::String("0".to_string()));
-    assert_eq!(eval("toString (-2.5)"), Value::String("-2.5".to_string()));
-}
-
-#[test_log::test]
-fn bool_to_string() {
-    assert_eq!(eval("toString true"), Value::String("1".to_string()));
-    assert_eq!(eval("toString false"), Value::String("".to_string()));
-}
-
-#[test_log::test]
-fn null_to_string() {
-    assert_eq!(eval("toString null"), Value::String("".to_string()));
-}
-
-#[test_log::test]
-fn simple_list_to_string() {
-    assert_eq!(eval("toString [1 2 3]"), Value::String("1 2 3".to_string()));
-    assert_eq!(
-        eval(r#"toString ["a" "b" "c"]"#),
-        Value::String("a b c".to_string())
-    );
-}
-
-#[test_log::test]
-fn nested_list_flattens() {
-    assert_eq!(
-        eval("toString [[1 2] [3 4]]"),
-        Value::String("1 2 3 4".to_string())
-    );
-    assert_eq!(
-        eval("toString [1 [2 3] 4]"),
-        Value::String("1 2 3 4".to_string())
-    );
-}
-
-#[test_log::test]
-fn empty_list_in_list_no_extra_space() {
-    assert_eq!(eval("toString [1 [] 2]"), Value::String("1 2".to_string()));
-    assert_eq!(eval("toString [[] 1 2]"), Value::String("1 2".to_string()));
-    assert_eq!(eval("toString [1 2 []]"), Value::String("1 2 ".to_string()));
-}
-
-#[test_log::test]
-fn list_with_multiple_empty_lists() {
-    assert_eq!(
-        eval("toString [1 [] [] 2]"),
-        Value::String("1 2".to_string())
-    );
-    assert_eq!(eval("toString [[] [] 1]"), Value::String("1".to_string()));
-}
-
-#[test_log::test]
-fn list_with_bool_and_null() {
-    assert_eq!(
-        eval("toString [true false null]"),
-        Value::String("1  ".to_string())
-    );
-    assert_eq!(
-        eval("toString [1 true 2 false 3]"),
-        Value::String("1 1 2  3".to_string())
-    );
-}
-
-#[test_log::test]
-fn mixed_type_list() {
-    assert_eq!(
-        eval(r#"toString [1 "hello" 2.5 true]"#),
-        Value::String("1 hello 2.5 1".to_string())
-    );
-}
-
-#[test_log::test]
-fn attrs_with_out_path() {
-    assert_eq!(
-        eval(r#"toString { outPath = "/nix/store/foo"; }"#),
-        Value::String("/nix/store/foo".to_string())
-    );
-}
-
-#[test_log::test]
-fn attrs_with_to_string_method() {
-    assert_eq!(
-        eval(r#"toString { __toString = self: "custom"; }"#),
-        Value::String("custom".to_string())
-    );
-}
-
-#[test_log::test]
-fn attrs_to_string_self_reference() {
-    assert_eq!(
-        eval(
-            r#"let obj = { x = 42; __toString = self: "x is ${toString self.x}"; }; in toString obj"#
-        ),
-        Value::String("x is 42".to_string())
-    );
-}
-
-#[test_log::test]
-fn attrs_to_string_priority() {
-    assert_eq!(
-        eval(r#"toString { __toString = self: "custom"; outPath = "/nix/store/foo"; }"#),
-        Value::String("custom".to_string())
-    );
-}
-
-#[test_log::test]
-fn derivation_like_object() {
-    assert_eq!(
-        eval(
-            r#"let drv = { type = "derivation"; outPath = "/nix/store/hash-pkg"; }; in toString drv"#
-        ),
-        Value::String("/nix/store/hash-pkg".to_string())
-    );
-}
-
-#[test_log::test]
-fn string_interpolation_with_int() {
-    assert_eq!(
-        eval(r#""value: ${toString 42}""#),
-        Value::String("value: 42".to_string())
-    );
-}
-
-#[test_log::test]
-fn string_interpolation_with_list() {
-    assert_eq!(
-        eval(r#""items: ${toString [1 2 3]}""#),
-        Value::String("items: 1 2 3".to_string())
-    );
-}
-
-#[test_log::test]
-fn nested_to_string_calls() {
-    assert_eq!(
-        eval(r#"toString (toString 42)"#),
-        Value::String("42".to_string())
-    );
-}
-
-#[test_log::test]
-fn to_string_in_let_binding() {
-    assert_eq!(
-        eval(r#"let x = toString 42; y = toString 10; in "${x}-${y}""#),
-        Value::String("42-10".to_string())
-    );
-}
-
-#[test_log::test]
-fn empty_string() {
-    assert_eq!(eval(r#"toString """#), Value::String("".to_string()));
-}
-
-#[test_log::test]
-fn empty_list() {
-    assert_eq!(eval("toString []"), Value::String("".to_string()));
-}
-
-#[test_log::test]
-fn to_string_preserves_spaces_in_strings() {
-    assert_eq!(
-        eval(r#"toString "hello  world""#),
-        Value::String("hello  world".to_string())
-    );
-}
-
-#[test_log::test]
-fn list_of_empty_strings() {
-    assert_eq!(
-        eval(r#"toString ["" "" ""]"#),
-        Value::String("  ".to_string())
-    );
-}
-
-#[test_log::test]
-fn deeply_nested_lists() {
-    assert_eq!(
-        eval("toString [[[1] [2]] [[3] [4]]]"),
-        Value::String("1 2 3 4".to_string())
-    );
-}
-
-#[test_log::test]
-fn list_with_nested_empty_lists() {
-    assert_eq!(
-        eval("toString [1 [[]] 2]"),
-        Value::String("1  2".to_string())
-    );
-}
-
-#[test_log::test]
-fn attrs_without_out_path_or_to_string_fails() {
-    let result = eval_result(r#"toString { foo = "bar"; }"#);
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn function_to_string_fails() {
-    let result = eval_result("toString (x: x)");
-    assert!(result.is_err());
-}
-
-#[test_log::test]
-fn to_string_method_must_return_string() {
-    assert_eq!(
-        eval(r#"toString { __toString = self: 42; }"#),
-        Value::String("42".into())
-    );
-    assert_eq!(
-        eval(r#"toString { __toString = self: true; }"#),
-        Value::String("1".into())
-    );
-}
-
-#[test_log::test]
-fn out_path_can_be_nested() {
-    assert_eq!(
-        eval(r#"toString { outPath = { outPath = "/final/path"; }; }"#),
-        Value::String("/final/path".to_string())
-    );
-}
-
-#[test_log::test]
-fn list_spacing_matches_nix_behavior() {
-    assert_eq!(
-        eval(r#"toString ["a" "b"]"#),
-        Value::String("a b".to_string())
-    );
-
-    assert_eq!(
-        eval(r#"toString ["a" ["b" "c"] "d"]"#),
-        Value::String("a b c d".to_string())
-    );
-}

fix/tests/tests/utils.rs

@@ -11,6 +11,13 @@ pub fn eval(expr: &str) -> Value {
         .unwrap()
 }
 
+pub fn eval_shallow(expr: &str) -> Value {
+    Runtime::new()
+        .unwrap()
+        .eval_shallow(Source::new_eval(expr.into()).unwrap())
+        .unwrap()
+}
+
 pub fn eval_deep(expr: &str) -> Value {
     Runtime::new()
         .unwrap()

flake.lock

@@ -8,11 +8,11 @@
         "rust-analyzer-src": "rust-analyzer-src"
       },
       "locked": {
-        "lastModified": 1773471952,
-        "narHash": "sha256-kIRggXyT8RzijtfvyRIzj+zIDWM2fnCp8t0X4BkkTVc=",
+        "lastModified": 1774076307,
+        "narHash": "sha256-v8axK9HGgVERw9oG3SKdsuE+ri0GPUZDyRBN4GLqQ1c=",
         "owner": "nix-community",
         "repo": "fenix",
-        "rev": "a1b770adbc3f6c27485d03b90462ec414d4e1ce5",
+        "rev": "556198cc6c69c0a13228a15e33b2360f333b0092",
         "type": "github"
       },
       "original": {
@@ -37,11 +37,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1773282481,
-        "narHash": "sha256-b/GV2ysM8mKHhinse2wz+uP37epUrSE+sAKXy/xvBY4=",
+        "lastModified": 1773821835,
+        "narHash": "sha256-TJ3lSQtW0E2JrznGVm8hOQGVpXjJyXY2guAxku2O9A4=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "fe416aaedd397cacb33a610b33d60ff2b431b127",
+        "rev": "b40629efe5d6ec48dd1efba650c797ddbd39ace0",
         "type": "github"
       },
       "original": {
@@ -61,11 +61,11 @@
     "rust-analyzer-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1773326183,
-        "narHash": "sha256-tj3piRd9RnnP36HwHmQD4O4XZeowsH/rvMeyp9Pmot0=",
+        "lastModified": 1774036669,
+        "narHash": "sha256-EWhsBSh/h1VcyLKXuTEyH8lNVB2ktuKVkqx8dkQ6hxk=",
         "owner": "rust-lang",
         "repo": "rust-analyzer",
-        "rev": "6254616e97f358e67b70dfc0463687f5f7911c1a",
+        "rev": "0cf3e8a07f0e29825f5db78840e646a4bb519742",
         "type": "github"
       },
       "original": {